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Electrical Gremlins

Old 05-06-18, 07:46 AM
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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

Last edited by Nemo128; 05-06-18 at 10:37 AM.
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Old 05-06-18, 06:13 PM
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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
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Old 05-12-18, 04:38 PM
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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.
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Old 05-20-18, 12:25 PM
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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!
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Old 05-20-18, 01:52 PM
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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
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Old 05-20-18, 04:07 PM
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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).
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Old 05-20-18, 04:46 PM
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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
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Old 06-09-18, 03:52 PM
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I noticed this strange not-stock-looking wire connected in the engine bay fuse box. The fuse shown inline with it was also blown.


I traced this wire and found it was going into the front relay box here.


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.


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.


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. -_-
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Old 06-10-18, 06:50 PM
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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.
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Old 06-10-18, 07:57 PM
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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
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Old 08-06-18, 06:43 PM
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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.
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Old 08-06-18, 07:22 PM
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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
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Old 08-15-18, 07:44 PM
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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.
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Old 08-16-18, 04:54 PM
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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
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Old 08-16-18, 05:13 PM
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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
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Old 08-17-18, 10:37 AM
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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.
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Old 12-22-18, 11:54 AM
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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.
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Old 12-30-18, 11:02 AM
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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.
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Old 12-30-18, 11:18 PM
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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.

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Old 12-31-18, 10:41 AM
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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...
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Old 12-31-18, 11:30 AM
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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.
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Old 12-31-18, 01:35 PM
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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.
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Old 12-31-18, 03:05 PM
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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!
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Old 01-01-19, 01:32 PM
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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.
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Old 01-01-19, 01:42 PM
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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.
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