Hey everyone,
I've dug into the archives, google, service manual, just about everywhere I could think of, but I still can figure out the problem with non-working gauge cluster, warning lights and cabin blower....

Quick recap...We did the emissions delete (which involved connection repairs to a few connectors; Oil pressure sensor, O2 sensor, injectors, and I had to resolder the male prongs onto the AIT sensor) minus needing to replace the exhaust from the turbo back everything seems to be running ok. I had to adjust the throttle cable and play with the TPS to get the idle smoother but for now she runs pretty well (in the driveway - throttle hesitates while shifting gears around the neighborhood)

But no gauges, warning lights, or heater/Ac blower...
I mentioned this in an earlier post which led me to sniffing out bad grounds. I replaced the ground from the intake manifold to the fire wall with a larger cable (the previous smaller one burnt up) and aside from the I only found one other bad ground, right below the brake fluid reservoir on the body which I included a picture. the ground was shotty and loose, so I cleaned it up down to bare metal and reattached. This ground however is on the 'starter harness,' which brings me to my first question.

Is the instrument cluster and other components I'm having issues with connected to the engine bay, starter, or any other harness under the hood? I know and understand that the sensors etc. feeding the instruments are on these harnesses but I figured they send the signals through the ECU to the appropriate gauge/warning light...

I replaced the CPU assuming I fried that along with the ECU when I hooked up the battery backwards because I read that the CPU sends signals to the instruments, no luck.. (I included an image of this)
I tried jumping the Leading and Trailing coils via the bullet connectors to get a reading on the Tach, no luck (I included images of the bullet connectors in case I used the wrong ones)
I noticed that the oil pressure sensor wire was broken and missing the connector, (luckily, I have a few spare harnesses) so cut the connector and some extra wire from a different harness to repair the connection, no luck getting a reading on the gauge.
While repairing the oil pressure wire, I noticed a white connector coming out of the starter harness in the same area with a broken wire, I have no Idea where the other end of the broken wire needs to go..? I included an image of this, any Ideas?
Also, I installed a kill switch for the fuel pump to eliminate flooding issues; I noticed next to the fuel pump relay (under the steering column) that I tied into for the kill switch, there's a white connector/plug, I've looked everywhere under the steering column for the other end and can't locate it, does anyone know what it's for?

I can't help but wonder what I'm missing.... Could it be a bad cluster, warning lights, and blower all individually at the same time? I looked over the fuse box (driver side kick panel) and all fuses are good, I tested continuity, pulled and replaced the meter fuse even though it was good. Is there a relay or something else in the cabin that they all run on that I'm overlooking? I've read about the bellhousing grounds playing a role in the tach but that ground seems solid too. Other issues to note are the wires/plugs that are broken/disconnected at the transmission where the shifter connects, thinking these are the shift and reverse lights - I don't know if or how they would play into my issues, but I'll get to them after I resolve my current issue. It seems like there should be a link between them all, I just can't seem to isolate it.
I do have a spare instrument cluster; my next step is to plug that one in and see if this powers up. Also, I was going to jump the blower motor to see if it's working on its own or not.

Feeling a bit lost now, and I know this topic has been beaten like a dead horse so I appreciate any and all assistance. Below are the pictures I made reference to above.

Thank you!

CPU

Coil Bullet connector

other Coil bullet connector

Shotty ground under the brake fluid res. (Starter Harness)

Mystery white plug next to fuel pump relay

" "

Plug coming off Starter Harness with cut wire, any idea where this wire needs to go?

repaired oil pressure sensor wire/connector with plug and broken mystery wire

another shot of the plug next to the oil pressure sensor wire, I don't know what this wire goes to, I can't locate the other broken end.

 

After some additional digging, it looks like the mystery plug next to the oil pressure sensor could be the conditioning capacitor wire (not needed?)

 

Yes, this is correct.

I'll re-read through your post again and try to think of some other things to check

 

I think we went over some of this already in your original post. I would have been easier to post to the original one so it is easier to track progress. Anyway, have you checked the bundle of black wire connected to the shock tower below the trailing coil yet? Those grounds are important, clean the connectors and the tower metal.

Under your dash has been hacked apart and put back together differently. The other end to that connector was probably cut off. That looks like a connector in my car that was used to splice in the aftermarket alarm system that was installed before I bought the car, possibly. Knowledge of the schematic or other will solve that one.

 

When I first looked a few weeks back everything looked ok. but now that I went back and scoped it out again, a couple wires had been wrapped with electrical tape going into a few of the plugs... could this be my culprit?

the disconnected plugs go to the Coil


taped wires


I unwrapped these two wires showing chaffing.

 

I wish that I can say that I know what exactly those do or that I agree with you that those are chaffed. Those wires look melted, sorry to say. What I do know is those wire caused a no start in my car once. Also, you are so close to that bundle of grounds on the tower.... any closer and they would bite you.

There is a pretty good chance the ground issues caused this, what looks like melted wires..... at some point.

You have some decisions to make, I can't make then for you. It looks like you know how to solider, I would follow the melted section back until you find good wire and splice the good harness on there. Or better yet, replace the entire harness with a better one, I know this is asking a lot. The decision is yours.

I had a car with melted wires wrapped with tape near a fuse box once, I do not recommend it. If you smell smoke, you'll know why.

By the way, get yourself some shrink tube for the splices. It cleans things up nicely and likely to have better insulating properties than a thin layer of poorly applied tape and it keep the moisture out. The green rot will get to the wire eventually if the moisture gets in. Some No-ox might help too.

 

Thanks! I guess I'll have to look closer for those grounds and yes heat shrink is a standard practice when I solder, I just forgot to slide a piece on the oil pressure wire prior to making the connection. I'll need to look around, I may have gotten an extra harness with the car, I got a bunch of spare parts with the purchase.
I'll keep searching for the grounds and clean up this wire mess, last thing I want is for trouble to migrate to the main relay.

 

Best wishes with the work ahead. I just soldered the same wire you just did for the oil pressure sensor. It wasn't fun with limited space and no helper, so good work there.
You can dig yourself a pretty big hole with these cars if you keep digging sometimes. Knowing when to stop isn't a skill I have perfected.
There are a lot of talented people here to help. Unfortunately, I am not one of them, especially the schematic because I haven't studied it much, I need a very large print on paper with an easy to reach legend.

Keep picking away at stuff and someone should be here to help.

 

Are these the grounds on the shock tower you were talking about

 

Yes sir, those are them. I t looks like someone was in the cleaning that up based on the scratches. Pull off the connector, unbolt the lug, clean the pins and the other mating surfaces. Clean some paint off the tower, clean all surfaces with scotch bright and treat with dielectric grease. or just clean it up some, put it back together and hope it holds up.

We need a schematic master on the thread.

 

This PDF will help you out tremendously, my brother and I recently removed his 88's entire body harness to strip out all the unused wiring. Long story short we were able to bag and tag each removed wire and connector along with leaving labels on the remining ones (each silver piece of tape was a label). I found it easiest to use a laptop/desktop and use the search function within the pdf file so you don't scroll back and forth for hours...if that makes sense. If your not familiar with wiring diagrams id urge you to read the first couple pages especial 50-4 where if defines how it labels the power sources (A,2,1,S,B) before you know it you will know the wiring like the back of your hand... holler if your really stumped on something. Good Luck!

 

Awesome, thanks for the share.

Update:
I installed the extra cluster I had and I'm pleased to announce that we officially have an working instrument cluster once again. Tach, boost, oil pres, fuel, temp, and speedo.
Now I can move onto the warning lights and blower motor.

Thanks everyone for the help!

 

the black "cut" wire is explained in the "related threads" if you scroll down past this thread below.

 

So, I spent some time investigating my HVAC issues trying to chase down why my blower won't work, and here's what I found.

I dug around in the archives looking for my issue and found some similar issues involving the Logicon, breakers, etc...
after reading through the posts and troubleshooting here's where I'm at.

I get power to the Logicon/climate control unit/HVAC (whatever its known as)
I pulled the vents above the control unit, and I can see/hear the doors opening and closing when selecting the different air direction buttons.
I disconnected and removed the blower motor, I jumped it with a battery, and it does work. However, there is no power at the plug when installed (which is my problem).
I did check the breakers in the fuse box, and they seem to be ok, no tripping.
I did the emissions delete but haven't removed the AC compressor yet, I'm not looking for AC just air movement thru the vents. Could I have accidently disconnected something that sends a signal to the blower?
When I select the recycle air button on the far right, I can hear movement near the blower motor (I assume it's a door opening and closing)
**One thing I read was that I should be able to hear a 'whirring' sound or similar when moving the temperature selection from cold --> hot and visa versa; I don't hear anything.

Could the HVAC resistor be causing the blower to not kick on?
Could the Logicon/HVAC control unit be bad even though parts of it are working?

I appreciate any and all assistance/direction.

 

there's 2 components that pass voltage to the blower motor and one is easy enough to test, the H-02 connector at the EXT-HI relay that sits beside the blower motor on the HVAC airbox has an input and out, the input is the I12 Blue/Yellow wire off the logicon to the relay, it passes through the relay to the positive output to the blower motor, unplug the blower motor and see if you get 12v on this I12 circuit, if it drops to a couple tenths of a volt when plugging in the blower motor then the issue is within the logicon itself or from the 12v input to the logicon from the ignition switch or A1/Battery in to the logicon. if you still get 12v on I12 with the blower plugged in but only a few tenths of a volt at the blower motor then your EXT/HI relay is faulty.

if the EXT HI relay is ruled out you can continue this test with the logicon slightly removed and monitoring those 2 inputs(A1 and Battery source) with the blower plugged in and not. if your input voltage to the logicon drops as well i would suspect the ignition switch as the problem but you likely would have other things not working in the car as well.

generally it is the logicon itself, but in most cases i have seen you would still get full blower speed if you set the slider to max and nothing in the middle range speeds. a bad swiper inside the logicon might be an issue too, try sliding the blower speed selector about 50 times or so to clean the resistor plate inside the logicon and retest.

the wording makes these tests seem daunting but they really are simple and only take a couple of minutes if you already have access to the logicon. the logicon can be repaired however i have no experience with that service, Icemark used to be my go to person for electronics repair.

 

This does sound a bit daunting, but if it gets me answers I'm all in. I'll start with the relay next to the airbox, seeing how I already have the blower out it should be easy enough to access.

Thank you!

 

the easiest way to explain it is to keep tracking back from the blower to see where you are losing the voltage, the logicon itself actually handles the full load of the blower motor, and also why it is the most likely component to be faulty.

 

These are the two relays I pulled down from beside the blower. looks like the red and yellow wire got a little warm at some point. You're saying I need to test the Blue/Yellow wire for 12v right?

 

i misread the wiring diagram, the Blue/Yellow is the control side of the relay, the Red/Yellow is the voltage coming to feed the blower motor, test that wire while plugged in with the blower unplugged and plugged in and see if the voltage drops significantly pointing to a failing relay.

the diagram is incomplete once it gets to the relay side and those connectors beyond the bulkhead that joins the main harness. that melted wire and connector points to high resistance though, either an issue with the blower motor, the relay or the ground circuit for the blower.

the ground should be a multi pin connector under the brake master cylinder area under the trailing coils, a pack of 4 or 6-ish black wires to a multi-pin ground block. i would check it anyways to make sure it's clean and solidly plugged in.


if the blower motor stalled with some debris it could have caused that connection to overheat and melt down the relay. once a relay gets hot enough to melt the housing the contacts inside begin to push away and cause a poor connection.

 

I'm not getting any reading at all...
I've plugged the relay back in along with the motor, tested the Red/Yellow wire using the cigarette lighter socket and the door jamb as a ground and nothing.
Same method with the blower unplugged; nothing...
And yes, I had the ignition in the 'on' pos with power going to the logicon.
I did reinspect the ground plug you mentioned under the coil, looks good and clean. I suspect that the relay left the chat when things got hot. I ordered a new Logicon and Relay.
Again, I know the blower works - I jumped it earlier today and the ting almost flew out of my hand.. I guess I'll wait to see if the new relay/logicon make any difference..?

 

strange, do you even get a click out of the black relay when sliding the blower motor slider to full on?

the circular pot is the power transistor for variable speed and the black relay is for max speeds.
Blower Motor not working, but relay clicks! - RX7Club.com - Mazda RX7 Forum

might just be worth waiting for your logicon to show up, i have a strong feeling that's what the issue mainly is.

 

No, I just tried while holding the two relays, no clicks no nothin.

After reading through the post you provided, I did try jumping the wires on the larger relay, and the blower spun. I didn't have any control over the speed or 'on or off' but it spun none the less.

I'll keep reading through what ever I can find while I wait on the Logicon to be delivered. Thank you again for your help!

 

the black relay is the full speed one, so it would seem it should have voltage on the red/yellow circuit if jumpering it works but the control side from the logicon isn't providing the pull down for the relay. if the logicon isn't working with the slider full to the right then it's looking more like a faulty logicon.

 

YAY! Got my Logicon today, kinda pissed that the harness was cut tho. Rather than soldering all the wires back together, does this wire 'plug' pop off the board, does anyone know if this plug is attached by pins? I don't want to pry on it too much and damage something-it looks like it should just unplug from the board. I'd rather be able to pop this off and plug in the one from my current 'suspected faulty' Logicon harness and avoid cut and soldered wires.

 

This is my spare, as you can see, I wasn't very careful removing this from my scrap car. I cut very little out of the car. So, there might be some splicing in your future.
It is possible one, two or maybe three of these come off that are connected. Hopefully, someone else can chime in.