Electrical Gremlins
 

Making this thread to track progress and ideas on my various electrical gremlins. Feel free to add any thoughts or advise if you think of something I should consider.

My 93's engine was fully rebuilt and upgraded. Many electrical issues remain for me to deal with. What I've found so far.

1. Turbo timer wasn't doing anything. Completely removed it for now.

2. The headlights pop up and do work. Pushing the stalk forward a bit causes the headlights to try to retract and turn off, but then pop back up and stay on. Either something is wrong with the stalk or there is a short somewhere.

3. The left turn signals operate normally. The right flash fast. The tail lights don't turn on at all. The dash lights don't turn on. Have checked fuses and bought one new TNS relay. Plan to replace all fuses just to rule that out.

4. A burned out spade in the ignition switch connector of the front harness is burned black. Bought a new ignition switch to eventually install once I know what caused this to happen. The burned out spade was originally connected to the turbo timer harness, which shows an equivalent burn on it. I plan to plug this directly into the ignition switch once I make sure things are ok electrically.

5. Sourcing a complete front harness. I think I might need to just replace the entire thing to rule out any issues. The PO did a real hack job on the stereo install too, so considering a redo of that harness.

6. Pulled out all bulbs. None are burned out. Plan to check continuity of all sockets to start. Reviewing the body electrical troubleshooting manual.

https://cimg0.ibsrv.net/gimg/www.rx7...25173fe7a3.jpg
https://cimg1.ibsrv.net/gimg/www.rx7...9cb97618d6.jpg

From the photos you sent, that turbo timer drew a lot of current!

Go through the wiring diagram manual systematically.

1. Verify that your wiring harnesses pass resistance checks between system elements.

2. The headlight and turn signal problems may be caused by the Body CPU. You can remove the circuit board from the CPU and inspect it for charring or burned up components. Since the turbo timer had a melted shell, then seriously look over the Body CPU for damage.

3. The right turn signal fast flash typically indicates a burned out bulb or poor conductivity between the bulb and socket. Since you said the bulbs are good then verify its socket. For instance, my right front turn signal was burned out but the bulb was good. I took the socket apart and cleaned up the corrosion that formed between the wire and socket. The turn signal came back to life and had no issues since.

4. Before you drop some serious cash on wire harnesses, inspect and document any problems first. The repair(s) may be simple. I would also recommend checking your speedometer circuit board for any potential problems with capacitor leakage. I have plenty of info about it on a few threads.

Best of luck to you and please keep the forum posted on your progress!

Cheers,
George

Yeah, get a new ignition switch module before you do anything else. A bad one will do all sorts of weird stuff. They're cheap, last I saw Rock Auto had them for a reasonable price and were in a Mazda part box.

Fast turn signals is either the flasher module in the CPU or a bad bulb. Possibly a bad tail light harness. The fast flashing is the flasher module telling you there is a burned out bulb.

Most of this stuff is probably pretty easy to fix. Just tackle things step by step.

Dale

Do yourself a favor and throw out the turbo timer. There is no need.

Nemo,

What type of bulbs to you have in the light assemblies? Are they standard incandescent bulbs or LEDs? If any are LEDs then you would get a fast flash on the side that has it because the current draw is considerably less than a conventional bulb.

Cheers,
George

Defly going to do all this. Not a short job so I need to make the time to do it. I'm going to check CPU2, might be the simple fix. My biggest concern right now is "finding" something wrong, fixing that, and then that going wrong again (for example, if CPU2 is a problem and I fix it for it, but another problem I didn't find/resolve damages it afterwards). I figure going through the wiring first is probably the safest initial step to confirm the connections aren't a problem. What do you think? I also thought about getting a JDM harness for cheap off eBay just to salvage the connectors to rebuild parts of mine.

Exactly! Ignition switch from Rock Auto is already in my cabinet waiting to be installed. I only want to make sure I don't install it before I resolve anything else that could cause the new one to have a problem or get damaged.

Done. Removed and I don't plan to put it back. It wasn't working anyway and everything is wired like crap from the PO, so I hope to resolve all of that over time. For example, my biggest pet peeve with car electronics is people who splice an aftermarket head unit into a car rather than use a harness when one is available. Drives me mad. If one isn't available I get it, but when it's a $10-20 part, it just irks me to no end.

So far I found all incandescents. No LEDs anywhere. I'll keep going through and make sure.

The battery was also relocated to the trunk of the car.

Nemo,

Thank you for the feedback. I'm glad to hear that you eliminated the turbo timer and verified that the bulbs are not LEDs. Here are my recommendations:

1. Disconnect the battery, remove it from the car, and place it on a battery tender (if you use one). I keep one on my FD all the time - that battery is 10+yrs old! Verify the wiring to and from the battery is sound, relocated in the trunk. Is the right gauge wire used? Does corrosion exist between connectors? Is the Ground wire connected properly - no breaks?

2. Pick the low hanging fruit! Replace the ignition switch. You already identified it as a problem and have the new part. Once replaced, check that problem off your list. Remove and inspect the Body CPU. First examine the flasher board for any damage then inspect the main board (the main board is the long one under the "surf board" panel). Damage may not be obvious therefore do not reinstall it into the car.

3. Perform resistance checks on the wire harnesses, refer to the wiring diagram manual Section X for more info. I would print off each applicable wiring diagram section, highlight the traces to test then check them off. This will certainly take time to complete but persevere. This procedure will remove all doubts in your mind that the harness is good to go. A break in the wiring may not be exclusively in the Front harness. It could be elsewhere - the Emissions harness, Instrument Panel harness, etc... Check the wiring from start to end point. Take note then continue until finished. Avoid going down the rabbit hole on the 1st problem - separate harnesses to find that specific fault. Note all the problems then see what they have in common.

4. Connectors can be sourced without purchasing a harness, JDM or USDM type. Again, save the expense on a new harness until you are certain that damage cannot be easily repaired. I have a thread about connector purchases.

5. Approx 90% of all electrical problems happen within 1" of a connector. Never discount the failure of a connector either!

Ask if you have more questions. Keep us posted on your progress!

Happy New Year,
George

I did two things recently. First, I pulled the front passenger blinker since I noticed it wasn't working at all. I found the shared ground connection to be totally bare, no insulation or heat shrink. The PO also did a hack job on the hot wires.

Second, I opened CPU2 and found what I believe to be at least one but possible two resistors needing replacement. They're R18 and R19 in the photo. The C2 capacitor also has some blackening on the left pad, but the cap itself doesn't look bad. I could replace it as a precaution. Sorry for the large image, I wanted to capture as much detail as possible.

https://cimg1.ibsrv.net/gimg/www.rx7...3df21a2c53.jpg

Nemo,

R18 and R19 are actually fine. That black stuff you see is actually acid (electrolyte) from the capacitor C2 leaking out. Clean off the circuit board with isopropyl alcohol and an acid brush or tooth brush. Pay attention to the solder joints of R18 and R19. They may look tarnished after cleaning. The solder joints still provide a good electrical and mechanical bond so don't mess with them. I would recommend replacing C2. Afterwards, the board should be good to go unless it has other gremlins. What does the rest of the board look like?

Cheers,
George

I broke out my old Hakko 808 and removed C2.
https://cimg9.ibsrv.net/gimg/www.rx7...6612c69e3a.jpg

I inspected the rest of the components more closely. I found C3 was completely detached from the board on the positive leg.
https://cimg0.ibsrv.net/gimg/www.rx7...a78b350c28.jpg

I removed it. Here it is.
https://cimg6.ibsrv.net/gimg/www.rx7...45af586a93.jpg

Did a cleanup with some alcohol and a toothbrush, and the board now looks like this.
https://cimg4.ibsrv.net/gimg/www.rx7...c55a2f3e77.jpg

Nemo,

Very good to hear! Well done on the visual inspection! You did a great job cleaning up the eyelets too. I presume you are no stranger to soldering components? What are the values of C2 and C3? Please remember to observe the polarity of electrolytic caps. The filled in half-moon on the circuit board denotes the negative lead.

Cheers,
George

Yep, luckily this has a lot more room than I normally solder. =)

Both 16V, C2 is 10uF and C3 is 220uF. Looks like I gotta wait for a DigiKey delivery to do this. I think these will do. Figure I'll purposely get the wider temp rating and 2000 hour lifetime caps.

https://www.digikey.com/product-deta...7-1-ND/4319714

https://www.digikey.com/product-deta...7-1-ND/3129694

Nemo,

Excellent! What other progress have you made with your wiring harnesses? While you are at it, now may be a good time to check your speedometer circuit board before the odometer blanks out. I met with 2 other members within 1 week who needed help in repairing them. BTW, I'm not trying to jinx you.

Cheers,
George

I replaced the caps and reinstalled the unit. Still fast flashing on the passenger side. I insistedi all the sockets and the bulbs work when I install them in the driver's side sockets. There's also a coolant leak I noticed, so another issue to deal with. I should really just get rid of the car, in 2+ years of ownership it's spent 2 in shops and driven a total of 40 miles. This was totally not worth it.

Nemo,

I understand your frustration with electrical problems. Especially when you inherit the sins from a previous owner. I encourage you to take the time to methodically take resistance measurements and you will be rewarded for fixing all the electrical problems.

Have you inspected the flasher CPU from the Body CPU? Remember, this is a separate card from the main board that you found bad capacitors. The flasher CPU controls the flash rate. However, since you still have one side that fast flashes, there may still be a problem with the wiring.

Please refresh my memory: when you test the turn signals, do you see the lights flash on the front AND back lenses? When the right side fast flashes, do you see both the front AND rear lights flash? Have you verified the turn signal sockets make a good connection and/or cleaned the corrosion from them? The front turn light assemblies typically get water intrusion than the rear and will corrode.

In an earlier post, you commented that the rear lights do not come on. What exactly do you mean by this? Do they not come on when you turn the combination switch (on the stalk) to Park or Headlight? If so, that is a function of the TNS circuit which flows through the Body CPU. After you soldered the new capacitors in place, did those lights come back on? BTW, TNS is an acronym for Tail, Number, and Side lights that references the lights when the combination switch is set to Park or Headlight.

If the front right turn signal does not flash then try this:
1. Remove the right side turn signal housing and unplug it.
2. Remove the left side turn signal housing and unplug it.
3. Connect the left side turn signal into the right side connector.
4. Test right turn signal for fast flash.
5. If no fast-flash happens with the left turn light housing plugged into the right side then inspect the right turn signal housing for proper connection.

Best of luck on your repairs!

Cheers,
George

Hi George,

I inspected the flasher, I didn't see anything. Maybe I'll pull it and give it another once over to be sure.

Right now, the passenger rear turn signal illuminates with fast flashing. The front passenger turn signal doesn't illuminate at all.

The running lights don't illuminate when the light switch is fully on. Headlights light up, but that's all. Dash lights don't light either.

This is what the PO did with the passenger front turn signal wiring. Maybe the splice job on the ground bypassing the connector is no good. The hot lines were also not soldered, just twisted and exposed with no insulation or heat shrink. I can solder and shrink those, and redo the ground.

https://cimg2.ibsrv.net/gimg/www.rx7...8b96bdfdd9.jpg

Nemo,

I suspected the fast flash was the cause of a lens assembly out. I don't think you can swap lens assemblies because of the wire splicing. That must indicate a pin is broken/corroded inside either half of the connector. Are these stock lenses or aftermarket? If aftermarket, which one?

NOTE: It is obvious that the splice job to the right lens assembly was poor. The exposed wires could easily cause a short to chassis ground.

The proper thing to do is to replace the connector. This way you know the repair is permanent and it is done right. They can be sourced online. I have a thread that covers connectors for the RX-7 of all generations. Take a look here: Electrical Connectors

If you want to take some pictures of the flasher CPU and post then I could review it. However, I suspect the main culprit of your fast flash problem rests with that right front lens assembly. How does the left front lens wiring/connector look? Make sure you inspect the inside of the connector.

As for the dash lights, have you verified the fuses are good? It is a good idea to frequently check the fuse box for any blown fuses as you diagnose multiple electrical gremlins. This helps to avoid chasing your tail. Could you explain more about the dash light problem? Is it a backlight (gauge) illumination problem, warning light illumination problem, interior dome & map light problem, a combination of problems, or another issue? Refer to the Diagram C-1a & C-1b for the Instrument Cluster & Warning Lights and Diagram I-2 (as in capitol i) for the Illumination Lights.

Do the same with the parking lights, aka TNS lights. Check for blown fuses first. Then refer to Diagram E-3 (Pg Z-58) in the wiring diagram manual. I would even suggest that you inspect the wiring at the tail lights as the 2nd step (1st step is to verify fuses). If the front lens assemblies were hacked then you may see a similar problem in the rear. Did the PO install an aftermarket car alarm? Did you remove it? Again, by looking at Diagram E-3, the potential problems to cause no TNS lights are: TNS relay, Body CPU (CPU#2), and CPU#1. CPU#1 is physically on the back side of the fuse box. Do not forget the potential of broken/shorted wires in this system!

Cheers,
George

Unfortunately I get to work on this car 15-30 minutes at a time, and I find myself rushing to make any progress. This is what's happened the last three times, all due to rushing.

First, I reversed the battery wires one day. Sure enough, 120A main fuse exploded. Went to Autozone a week later, $3 spent and I have a main fuse. I got home, fitted it just to make sure I got the right one, pulled out the battery, hooked it up to my tender, and was done.

Then another week later, I hooked up the battery... notice I didn't say I finished bolting back the connections to the main fuse. After a loud spark, one of the connectors that go to the main fuse was spot welded to the intercooler piping. Disconnected the battery, hooked it up to my tender, and went to work on the connections for the main fuse. Which of course were burning hot to the touch, so I waited for them to cool down.

Then I realized, I don't even remember from weeks ago how the main fuse was connected. Here's a pic to explain.
https://cimg0.ibsrv.net/gimg/www.rx7...942f30a04d.jpg

The red arrow goes on the left side. The thing I can't remember is, the blue arrow connections. I see two eyelet connectors. But I don't remember which leg of the connector they belong on. I don't know if they were originally as I'm showing them here, that's how I happened to do it today and realized I'd rather not guess it and invite more risk.

The reason I'm focusing on this is because I need to start the car and see where this coolant leak is coming from. The whole engine was rebuilt and it drove 40 miles (from a body shop to my house) so I don't get why there'd be a giant pool of coolant on my garage slab. Before bothering with more of the electrical issues, I want to deal with that coolant leak and it seems to only happen when the car is running.

Nemo,

Sounds like this is a textbook example of haste makes waste. Patience is necessary when it comes to testing wires or connecting/disconnecting them. I would also encourage you to inspect the Body CPU (all boards inside) for additional damage that may result from cross-connecting your battery. How do I know? This happened to my Vert: Battery Reverse Polarity

Do those wires/eyelets at the Blue Arrow connect to chassis ground? What is underneath all that tape? What type of tape is that? Is your battery relocated to the trunk or storage bin? Is that Red Arrow pointing to a component that attaches to the intercooler piping? That piping should have no electrical connections nor serve as an electrical ground.

I would disconnect your battery first and then break out a DMM to read resistance of these wires to figure it out. Otherwise, you may wind up killing another battery, blowing another 120A fuse, and causing more damage to other electrical components. Lastly, draw a schematic of your battery connections and keep it with your manuals to prevent future cross-connections.

Cheers,
George

The red arrow is just the connection to the main fuse. It was disconnected and resting against the intercooler piping.

The battery is located in the trunk, previous owner did that. Plenty I don't know about what he did to the car.

Nemo,

Make sure that you identify which cables connect to the Positive and Negative terminals of your battery. Using a DMM (Digital Multimeter) will help you. I get the impression that these 2 wires in your photo are not meant to connect to one another. Do you know what is under all that tape? It would be very important to identify the Negative cable and Positive cable of the original battery location then track them to the battery's new location in the trunk. These cables are typically thicker than the others because they must deliver higher amounts of current, especially to the starter and charging circuits.

Cheers,
George

Something weird I see. The fuse space above the main fuse is shown as unused on the cover. Why is there a fuse in that position on my car?

Prior to these issues, the car ran and drove so I don't think having a fuse there adversely affected anything. But what I'm trying to figure out is, why is it there in the first place?

I also noticed on inspection that it was blown anyway.

Nemo,

First, did you reconnect the battery properly? How did you solve that problem? The answer to your mysterious fuse rests with the PO. Was the PO a forum member? Maybe you could read some of his old posts to indicate what was done to the car? Can you inspect the fuse holder from below and trace back the wires? Do these wires look OEM? If the mysterious fuse was blown then there must be a reason for it. What size is the fuse? It could be for an upgraded fuel pump, stereo, or something else that would need high current. Additionally, did you fix the turn signal and headlight problems after the you found the sketch wiring and repaired the Body CPU? Lastly, did you replace the ignition switch?

Thank you for updating the forum!

Cheers,
George

Today was an interesting day. Last weekend, I was able to get the car started back up. Engine ran fine, and no damage from the battery mishap seems to have occurred. I also managed to identify the sources of the coolant leak and tightened up some fittings. Hopefully that's all it needed.

I also replaced the ignition switch with the one I picked up from Rock Auto, just cuz why not.

On to today's electrical investigation. First, I opened up that that crimp connector that was on the passenger side headlight just to see what was in there. This is what I found.

https://cimg5.ibsrv.net/gimg/www.rx7...892d292325.jpg

This was just two wires twisted together with some random third wire section thrown in... just cuz? Who knows. Thanks PO!

So, I did some testing with a test light and I was able to make bulbs light up but still with fast flashing. I then went to the Body CPU to pull it thinking I need to open it up again, and I took a closer look at it... and noticed this.

https://cimg9.ibsrv.net/gimg/www.rx7...e950da3d59.jpg

Two wires going to the connector were in need of repair. One was completely cut through, the other was only connected by two strands of the wire.

I broke out the soldering iron and head shrink, went to work, and plugged it all back in. Still fast flashing on the passenger side, but those wires needed to be addressed anyway, so I felt a lil accomplished. Until I noticed something odd. Whenever I see black electrical tape where it probably doesn't belong, it always makes me pause. This is what I saw for the two wires going from the light stalk to a connecter under the steering column when I removed the tape.

https://cimg3.ibsrv.net/gimg/www.rx7...2399706794.jpg

Now I know they did some weird things on this car, but I doubt that was factory spec. I unfurled this tangled mess of wire, and I found that the two wires coming from the light stalk were bare and touching while some random bundle of stranded wire was just wrapped around them. You can see me holding up that bundle in the bottom left of the pic.

https://cimg6.ibsrv.net/gimg/www.rx7...4f6faa1d47.jpg

This was... just disturbing. Even more confusing, my headlights were not popping up and turning on reliably already. Once I undid this and separated the wires as you see above, the headlights refused to work at all. I rubbed those two wires together, and it would make the lights then work. I found this odd. If those two wires are in fact supposed to touch, why wouldn't they just, from the factory, jumper them at their ends and use a single wire. This seems like an unreasonably strange way to do this, if in fact it's supposed to be like that. I'm hoping someone can tell me from their stock working lights if in fact those two wires should be bare and touching along their length before they go into the blue connector. I'm also going to inspect this further. For now, moving on.

I finally got fed up with this flashing issue... I decided, with some encouragement from the wife, to just cut off the male end of the 3 pin connector feeding the turn signal on the passenger side. At this point, I really felt something could be wrong with the connector itself. I moved the whole light section with the female connector to the driver's side, and it worked fine. So, I grabbed the wire cutters, snipped it, did some quick twists with the turn signal socket and the test light... and there was no fast flashing. :burn:

So, the source of the passenger side fast flashing was this connector alone.

https://cimg2.ibsrv.net/gimg/www.rx7...d360c389d0.jpg

I want to replace this connector. Hopefully I can find this connector. If not, I'm going to replace it with any 3 pin connector male/female pair I can get my hands on.

I still need to figure out the gauge cluster lighting, but I feel like this was a good breakthrough. At least I can resolve the fast flashing now. Some progress is better than no progress. Tomorrow I'll try to think about the gauge cluster. It's really the only thing preventing me from driving now since I can resolve the fast flashing.

Wooow, that is some piece of work my friend. It takes patience to tackle electrical issues. Good job you are doing..

I found the appropriate connectors on Gen2's link. Ordered male and female. I'll repair that as soon as they arrive. Today, on to the gauge cluster! Specifically the issue with the cluster is the backlighting. The odo works and lights up, all warning lights work, just the gauge backlighting doesn't come on. I wonder if it could be the dimmer switch and if there's a way to test that without another dimmer handy.

Also need to find the 6 pin connector that goes into the ignition switch. The 6P250-L here might be it: http://www.easternbeaver.com/Main/El...onnectors.html Male 6P250-L

Nemo,

I'm glad that you were able to order a replacement set of connectors for your turn signal. You should be able to find the other connectors you need from the links in that thread. Keep up the good work on repairing those hacked wire harnesses. Just solve one wire problem at a time and it should be right as rain soon enough. It takes a tremendous amount of patience to repair a wiring problem. You should be able to apply for sainthood after solving all of your wiring issues! Was an aftermarket car alarm installed in your FD?

Have you removed the instrument cluster yet? How does the flex print look on the back side of the cluster? Coincidentally, I started a thread about that flex print. There is more content on the flex print to follow so keep your eyes peeled! In the mean time, if you are having problems with cluster back lighting, check out the dimmer switch first. Remember, the dimmer switch uses pulse width modulation to control the brightness of the gauges & cluster.

Keep us posted on your progress!
Cheers,
George

I do have an idea to source brand new connectors for the ignition switch. The HKS ZT-2 turbo timer harness has one. They're about $15-20. Buy one and either cut it to pigtail it or unpin it and repin the stock wiring into it. So far, best option I've been able to find. Since I have one of those harnesses, I'm going to attempt that.

Some quick updates.

After a few shipments from DigiKey and bmotorsports, the lights are no longer fast flashing. I rebuilt the passenger side turn signal harness like (or better than honestly) OEM, and it's all good.

I salvaged the ignition switch 6 way connector from the HKS harness, rebuilt it with new terminals, and plugged it back in. All seems well, and there's no longer a burned terminal on there.

I still need to figure out why the headlights refuse to work again. I also grounded the R/G for the dimmer switch and the gauge cluster still didn't come on. I measured the V on the R/G and the R/B wires for the dimmer. The Vs reported are 0.81V for R/G and 0.15V for R/B. That doesn't seem right. On to the wiring diagram!

Nemo,

Good to hear that your turn signals are repaired. Well done! Did you take any photos of the repaired wires & connectors?

Regarding your headlights, refer to the Body Electrical Manual (BEM), Section E for troubleshooting your headlights. This may sound like the same problem but they are different: Do your headlights come on when you turn on the combo switch on the steering column? Do your headlights pop up when the combo switch is turned on? If the headlights do not pop up then look down into the nose of the car; do the headlights come on?

As for the Dimmer switch, taking a voltage measurement will not work. You would need an oscilloscope because the brightness of the bulbs are controlled by a pulse-width modulated signal. That means the bulb brightness is controlled by the "on" time of a pulse. This length of a pulse is known as pulse width. The longer the pulse, the bulb's "on" time is longer. The shorter the pulse, the bulb's "on" time is reduced. Using a DMM on this circuit, especially reading DC Volts, will not show much. I am unable to cite a troubleshooting reference in any manual right now. Looking at the schematic is helpful to a point - identify wires but will not help in testing the outputs. It is also worth mentioning this could also be related to the headlight problem. The interior illumination is controlled by the TNS relay. That relay is part of the exterior lights.

Since you had some hacked wires at the turn signal and ignition switch, I would recommend that you visually inspect all wires associated with the external lights (headlights & TNS) and combo switch. It is very rare to have problems in the illumination lights circuit.

Cheers,
George

I didn't take pics but I can.

I jumper wired the R/G and ground on the dimmer switch's connector to bypass it completely. I think that should make max brightness. I also put a jumper wire on the cigarette lighter connector. No dash lights still.

The headlights do pop up and work, but only if I touch those two exposed (R and G) wires from the combination switch (3rd and 4th pics on my last post with pics). I just find it odd that makes it work. It doesn't seem from the wiring diagram that R and G should be connected between the combo switch and its connector. The black wire has a small slice in it, I can easily repair that.

Another thing I didn't remember to note until now. The side marker lights don't work, front or back. I did replace the TNS relay (bought 2 just to have them since there are 2 in the front relay box).

Nemo,

Have you double or triple checked your fuses after you repaired your turn signals? Don't assume it's good because it was checked hours/days/weeks ago. Since you inherited a wiring mess, it would also be a good idea to check for stray grounds in the external lighting system. For example, those exposed wires from your combo switch should be traced back for any other surprises. The reason why you are so surprised is because there are no documents that track all of these electrical alterations.

Do keep us posted on your progress!

Cheers,
George

I noticed this strange not-stock-looking wire connected in the engine bay fuse box. The fuse shown inline with it was also blown.
https://cimg3.ibsrv.net/gimg/www.rx7...64e7c16179.jpg

I traced this wire and found it was going into the front relay box here.
https://cimg0.ibsrv.net/gimg/www.rx7...0c3c96185e.jpg

So of course, opened up that crimp connector and found a horrible mess of wire. I found the original wire, cleaned, spliced, heat shrunk, tested continuity to the fuse box, and considered that done.

Then... well, I did this.
https://cimg0.ibsrv.net/gimg/www.rx7...65341c28e6.jpg

I did it because the PO hacked up the instrument harness to install a stereo, and I wanted to undo that mess. Here's what the instrument harness looked like.
https://cimg0.ibsrv.net/gimg/www.rx7...a468a89c30.jpg

I picked up another instrument harness from the For Sale section, it arrived in good condition, and I hooked it up today. What I'm trying to decide is, should I relocate the grounds? I notice the grounds go to the crash bar, but that also makes it more annoying to pull the dash and to test the harness prior to reinstalling the dash. I think it's worth it to just relocate the ground to the chassis somewhere. If you think this is a bad idea, I'd love some input on why.

Swapping the instrument harness didn't resolve the gauge cluster backlighting or the combo switch issue, but at least it removed that mess from the radio connector. I'm still tempted to just replace the rest of the harnesses while the dash is out. I found another broken wire that I repaired which was going to the rear of the car on the driver's side.

I also noticed, there's no longer any beeps coming from the car. Before I removed the dash, the car would beep when you turn the key to on. I hear nothing now. Wonder if this is due to the grounds not being connected or something else entirely.

The interior instrument lighting is the last thing I need to resolve. Once I do, all the interior covered bits (dash, seats, wheel, door panels) are going to my upholster for some sexing up. But, I'm not sending it off until I know the car is electrically 100%. The intent is going to be to get the parts back and put the car all back together. And drive it. After 3+ years. -_-

Interesting find today. The person I bought the car from is a member here. They haven't signed in literally since I bought the car. I didn't find it on here, I found it on Craigslist.

The username is Rx7xtasy. I'm digging through his posts to see what could have possibly been done to this car. Sure enough, it looks like someone that was not too good at this and it seems a user named Lance worked on this car. He also got harness off here at some point. Interesting to see though, since I know a little more about the history of this thing now.

Nemo,

Holy cow! That is one mess of wires. I do not envy your project. Patience in wire repair will have a big payoff once it is done. Good detective work on your FD's history!

In my opinion, I would not move the ground points from the crash bar. It may be more of a pain to remove and install however, if those spots worked for 22+yrs then it would be good for another 25+yrs. Clean up any corrosion around those ground points then reattach/reinstall crash bar and ground wires. If you want to protect those ground points then apply some dielectric grease on the connection AFTER the ground wires are connected. Dielectric grease is an insulator and therefore will not conduct electricity. It will reduce the amount of corrosion caused by air exposure.

The beeps originate from the Body CPU. When the 20-pin connector is unplugged or its ground removed, it will no longer beep. More importantly, the Body CPU will beep when: the key is left in the ignition cylinder, parking/headlights left on, seat belt not connected, engine over-revolution, and/or coolant level is low. Some of these will beep, beep at you while others will beeeeeeeeep at you. The BEM, Section C2 (Body Electrical Troubleshooting Manual) discusses the alarm function of the Body CPU. Look for the table marked as "Warning Alarms".

Cheers,
George

Has anyone seen/found an electrical schematic for the internals of the Body CPU? I know the manuals show the pinouts and circuits it connects to, but what about the schematic for what's inside the box? The PCB seems multi layer so there are traces that simply aren't visible.

I ask because while I've replaced some capacitors, I'm convinced the problem with it is bigger than that. I'll explain more once I do some more work on it.

Nemo,

Until someone reverse engineers a schematic from a Body CPU, the answer to your question is an unfortunate "no". A schematic does not exist. Its secrets are well kept by the original Mazda engineers. The board is dual-layered: traces run along the backside and topside of the board. Would you care to elaborate on the repairs to your CPU #2? What capacitors did you replace? Do you have any photos to share? Did my reference to the BEM help? What specific problems are you seeing with the Body CPU? Have you verified the problems are isolated to the Body CPU when compared to a known good unit? How much progress did you make from that mess of wires (in past photos)?

Cheers,
George

Quick update. The electrical troubleshooting guide helped me resolve the headlights completely. I had to remove some bypass wires the PO made, repair the combo switch harness, take apart the turn signal stalk and clean up the contacts, and the headlights are 100% operational.

But, the dash lights still didn't work. The troubleshooting manual led me (correctly) to suspect the harness between the 15A Tail fuse and the TNS relay. So, I removed the driver side headlight and found that the W/G wire going to the TNS from the 15A Tail was literally burned right through and broken. But then I suspected there could be more damage, so I removed the fender liner...

What I found (pictures will be posted soon) was that the front harness from the interior fuse box to the front of the car was essentially burned and fused all together. I removed the loom and black tape to find charred wires, fused insulation jackets, and foot long sections of the R/B and W/G wire without any insulation at all and touching. It looked like the circuit got too much current and just caught fire. It's totally F'd.

I suspect the fact that I found a 25A fuse for the Room (which is supposed to be 10A) to have played a part. I also found burned to bare strands wires from JB-07 of the interior fuse box. In short, the front harness needs to be repaired.

I'm now both looking for one here (time is money and this is going to be a lot of work) and going to start cataloging the wire colors to rebuild it. I like to keep factory spec wire colors, so I'll need quite a few. I found more than just the W/G and R/B wires burned through, so it's a lot to do.

Lastly, I fully removed the front harness from the car. It'll be easier to work on it out of the car. With the dashboard and fender liners removed, it's actually very easy to remove the front harness entirely. The dash removal was the hardest part, but since I already took it out a while ago, it was pretty easy.

Here's the damage inventory for tracking (wires that are damaged in the front harness):

GY - G/B - W/G - R/B - BR/W - P/B - BR - W/L

Nemo,

Excellent work isolating the fault to the front wiring harness! Bravo! I would not be surprised to hear that 25A fuse wrecked havoc on the electrical system. This is a good example of "never replace a fuse with a higher rating than the original circuit!" It sounds like you are very patient in rebuilding the harness. I would love to see photos of your work! Have you considered replacing the entire front harness with a new unit because of this extensive damage? After all, it's already out of the car and it would significantly reduce the repair time. The original harness could be a backup. Have you verified the other fuses are the right amperage for each circuit? When looking for parts, have you reached out to Ray Crowe or Fritz Flynn?

Again, congratulations on solving the problem to your dash and headlight woes.

Cheers,
George

I'm looking for a front harness but new simply isn't available. Ray doesn't have any. The best I'll get is a pull from one of the part outs, but while waiting to get one, I may be finished with the repairs by the time one is available.

I found a company that seems to sell nice GXL wiring by length. https://4rcustomswire.com/ They have all the colors needed too. I'll throw up some pics soon. Also going to measure the terminals in the connectors to see if I can just make all new wires from end to end rather than splice into the existing wires close to the connectors.

Well, it's been a while, but since my last post, I rebuilt the front harness and worked out all the electrical issues. Today I went to finish up putting the car back together, and as weird as it seems I'm having trouble getting the driver side mid guard reinstalled. I bet it's simply how the front harness is routed, but I can't get it back in. I'm worried that forcing it is going to crack that brittle crap plastic.

Once I get the mud guard in, that's pretty much it. The interior needs to go back together, dash reinstalled, and fire her up to finally drive normally. That damn mud guard though.

The car is (exterior) all back together. I tried to start it today, but I get nothing when I turn the key. Noticeably, I remember hearing the fuel pump prime previously, and that doesn't happen now. I also don't get any click, any attempt to turn over, nothing.

The interior status is, the dash bar is installed, the gauge cluster is not installed, none of the interior indicators are installed. The connections to the ECU (PowerFC) are all hooked up and the fuse box is complete with nothing blown. No fuses are blown anywhere, and all relays check out as functioning when hooked up to a power supply externally.

I'm going through what I can to see if I can identify why I get nothing when I turn the key, but if anyone has any ideas to try, please comment. I'm next going to try bypassing the security relay H302 and also get the battery tested for its cold cranking amps. Although I think if it was the battery or the security relay, the fuel pump would still prime at the least and I'd get some clicks like I read in other threads.

When my alarm relay shut off, I couldn't hear anything when I turned the key on, so I thought I had a bad solenoid. It was the alarm relay circuit.
It's so easy to just unplug the 2 alarm related connectors that I would try those 1st and leave them unplugged until you're finished working on the car,
because leaving your hood and/or doors open for awhile will trigger that relay. Your horn would sound a few seconds at a time for about a minute if working..
Good work by the way,and sorry you inherited someone else's mess.
Some of your side marker lights might stop working because they share circuits with those unplugged connectors.
Sorry I don't remember which 2 connectors, it's been a few years, so search one of the several threads outlining the disabling procedure. At a minimum you should hear your solenoid click once security connectors are off,
but your car should start if that circuit is now OK.

I removed the H302 alarm relay and connected the two wires for it like the bypass part sold by Banzai. I also bought a new AGM battery since the one that was there was very old and tested negative. Still nothing. I do hear a faint single click when I turn the key to ON (different click than the cylinder clicking forward when I turn the key). No fuel pump prime like it did previously.

I also have the trunk and hood propped open. I didn't think this would matter but I'll try closing both. Quickly running out of ideas short of the hours it'll take to test the various parts of the circuit one by one with a multimeter. I just want this car running normally already, years down the drain on this worthless project that seems to never end...

Nemo,

I'm sorry to hear that you are plagued with wiring problems still. How did the front harness replacement go - did you replace it or repair it? Once the harness was installed in the car did you verify that all connections went to the right places? Have you taken any resistance measurements in the starting circuit since this new issue surfaced? What have you checked? The trunk and hood open shouldn't affect the start-up process of the car unless there is an aftermarket alarm installed.

This may be easier said than done but...be patient! You found a major problem in the electrical wiring. Other electrical gremlins may still lurk about. It will take time to sort it all out. The fruits of your labor will taste sweeter once properly tended to.

I repaired the front harness, and from what I can tell it went perfectly. Everything that visually didn't work before now works. All interior lights, side markers, brake lights, headlights, everything is functioning as they should.

I unplugged CPU2 completely and connected the two wires for the alarm relay, still same result. Fuel pump doesn't prime, nothing happens. I think I'm down to basically checking every element of the starting circuit to figure out what's happening. I wish there was some more methodical straight forward check then simply, check each connection on each wire to see where the power is flowing or not flowing. That's not going to be a short process.

I appreciate the encouragement but I'm well out of patience at this point. I've spent tens of thousands and a few years to have a car that's driven 40 miles (from the shop that rebuilt the engine back to my garage) and been nothing but a source of stress. An epic waste of time/money, no other way to think of it.

Hang in there, Nemo!

I had to double check what year your FD is. I'm looking at a 93 wiring diagram manual (WDM) so I don't steer your wrong. There are some differences in the CPU#2 schematic; that's why I referenced it. What connector & wires did you bypass for the alarm relay? Is that the starter-cut relay? The wires to jumper should be L/W and B/L from Connector A1-03 (see Diagram A-1, Pg Z-24 of WDM). You may also need to verify the Starter-Interlock Switch (aka clutch interlock switch) works. That switch may not be properly adjusted and it would prevent the engine from cranking.

Regarding the fuel pump, you could test it at the Diagnostics Connector. Place a jumper (paper clip) between F/P and GND. When the ignition switch is placed to ON then you should hear it run and pressurize the system.

Keep us posted on your progress!

May you and family have a happy new year!

Thanks George. Well, I solved that. It was quite stupid really. I didn't connect the B/L wire to X01, which is what feeds the ignition switch. Connected that, and she churns hard.

But, it doesn't turn over. It cranks hard for a while, not whirring or sounding strained. It just doesn't kick over.

For context, the car was running when I got it back from the engine builder. It was last fired up successfully in the summer sometime, maybe June or July at the soonest. And it fired up strong. Since then, it's sat idle while I worked on the electrical issues.

The battery is brand new (Bosch Platinum AGM Group 35 bought two days ago) and fully charged. There's also no hesitation/strain on the cranking, it's cranking strong as this summer. It just doesn't turn over.

But hey, at least that's major progress. The car tries to start! It just doesn't finish.

Nemo,

See, you are making progress! Since the car doesn't want to kick over, remove the spark plugs and inspect for wetness & fuel vapor. If you smell fuel then the engine is flooded. Perform de-flood procedures to correct it and it should start. You may want to verify that you get spark coming from the coils first. As always, make sure you check all fuses, especially the EGI fuse when diagnosing no-start problems.