Third Generation F-Body Message Boards - Electronics

Holley transmission harness routing

formularpm — Fri, 29 May 2026 17:55:38 GMT

Hoping someone has some experience with this. Going to be switching from Holley HP to a Dominator, and need to figure out how to route the J4/P4 harness out of the interior and down to the trans.

I still have all of the HVAC equipment so can't use the A/C holes, the engine and chassis harness is using the passenger fender hole, and I'd prefer not to drill any 1.5" holes if possible.

Anyone have a good solution for this?

body harness diagrams 91-92

whit81084 — Thu, 28 May 2026 21:41:26 GMT

I have a 91 or 92 z28 im trying in restore and needing body harness diagrams etc. I am wanting to cut out the VATS and Air bag modules from the harness.

Pop up troubleshooting help

Michaelknight85 — Wed, 27 May 2026 23:56:48 GMT

I just picked up an 85 trans am project and I�m having trouble getting the pop ups to work.

It was missing the isolation relay when I bought it. I put a new one in and now the drivers side works perfectly but the passenger side only works down. If I manually raise it then turn the headlights off it closes right away, but absolutely nothing when I turn them on.

I tried testing the voltage of the green wire that goes from the actuator relay to the motor. It gets 12 volts when they�re locked out at the top, but if they�re down it�s barely anything(.04-.06). A new actuator relay didn�t help so I�m assuming it�s the connector. I tried cleaning them but still nothing.

These are the connectors before I cleaned them. Am I right in thinking that�s the problem? Where�s my best bet for finding one if so? I�m pretty new to diagnosing electrical problems so I�m not sure if I�m thinking about this right

1984 Rear Defrost fuse location

decurl — Tue, 26 May 2026 20:09:01 GMT

Hello Everyone, I have no power to my rear defroster switch at any time with key or and car running. I've checked the fuse panel and it does NOT contain a fuse for the RR-DEFOG. The cigarette lighter does work. Can someone please tell me where I can find the fuse for the Rear Defroster on a 1984 Z28. I've looked under the drivers side dash and do not see anything even though I am probably looking right over it. There seems to be some differences between the years so I am interested in where this is located on a 1984.
Thank you,
Dave

under hood light bulb

Spenc — Sat, 23 May 2026 21:30:45 GMT

found the overnight battery drain. hood light on this 84 was saying on, pulled fuse but any ideas on tracking down the cause. Thanks

Hei modules

Bill Chase — Sat, 23 May 2026 17:19:00 GMT

Does anyone make a decent 8 pin replacement module now days?
been helping a buddy with his 100% stock c4 corvette, only exception is msd 6al box. Cold starts, and keeping the plugs clean have improved. When the modules fail we are not seeing accelerated wear of the cap,or rotor. and it seems like every 18-24 months the module just dies.

Advance just swaps out the distributor, but it's annoying. We had hoped that getting rid of the old large cap hei would help, but same scenario. The 7 pin and 8 pin hei modules are just garbage now days.

Any suggestions?
should point out, the car is garage kept in Michigan, sees maybe 500 miles a year of use, not seeing rust or corrosion when they fail. They just die, dead giveaway is no tach movement when they fail.

Dash Wiring

upstateRich — Thu, 21 May 2026 14:12:07 GMT

Is the main wiring under the dash from the drivers side going to the passenger side supposed to go inside the plastic just under the windshield.

Removing power mirrors and wiring from salvage car

DigitalDan3 — Wed, 20 May 2026 15:35:01 GMT

I am going to be getting a bunch of interior parts from a recently wrecked 1990 firebird that has a beautiful interior. My 1988 Formula does not have power mirrors but the salvage car does. I really need the door panels for my car. I know the handle styling is different. The new to me driver side panel won't have a provision for the manual mirrors but I think I could easily cut the hole and purchase the trim if I go manual or use my current trim. I am going to be taking out the carpet in the donor car as mine is ruined. Car sat for 19 years with the window cracked. Water puddled in the driver side rear passenger well and eventually rusted through. I'm going to be replacing that part of the floor. The window being cracked open ruined the door panel too. No other rust on the car except battery compartment which I have seen on many salvage cars. It's a southern car that has not seen salt.

What is involved in getting the wiring harness out of the donor car and where does it route through. I think I read the mirrors have a plug to the wiring harness in the kick panels. Does the passenger side mirror wiring run across the top of the dash?

Any guidance would be appreciated along with instructions. I just want to be prepared ahead of time for what's involved and is it really worth it.

Thanks,
Dan

Mini starter wiring

iroczz89 — Tue, 19 May 2026 16:37:36 GMT

Can someone please confirm where all of the wires go on my new mini starter!

Radio Conversion

69-er — Mon, 18 May 2026 15:26:09 GMT

I started researching to find someone to convert my ERS radio in my 83 to modern specs, (Aurora receiver w/bluetooth, hands-free, etc), a month or so back but didn't find what I needed. There are several companies out there that do these conversions, but they tend to be for older units and not all repair cassette decks.

Has anybody got theirs converted and had their cassette player restored?

Thanks!

87 GTA- headlight issue?

Boostmaster — Mon, 18 May 2026 13:49:46 GMT

Actually headlights work fine. They go up and down no problem.

The issue is when I attach the battery (it's out of the car while we rebuild)- the motor on the right side spins and makes noise for a few seconds. That's it. I'm sure that's not normal. I even purchased the little plastic pellet bushings just in case...
Are they maybe on their last leg or am I looking for another electrical issue?

87 GTA 5.7L- Fan relays?? Electronics guru's needed

Boostmaster — Sun, 17 May 2026 17:12:52 GMT

Working on this GTA and the fan relay's by the front Right headlight housing have been cobbled with wire nuts and speaker wire! Looking through the factory manual to see if we can figure out what happened. Guessing a fan stopped working and the PO tries some sort of workaround.

Right now we have 3 Black wires with the red stripe all cut and we're not sure if they all attach together or not. Also the tan with white stripe wire looks to have 2 wires plugged into the same spot on the plug.

Finally, on the other side of the engine the green wires for the A/C compressor had some loose tape, When I pulled the tape there looks like a small resistor jumped across the pins. Never seen that before. Not sure if it is correct or not.

Can anyone help us out here? Maybe some pics of what these things are supposed to look like?

TIA

T56 and SGI-100bt

Mags_Gen21 — Fri, 15 May 2026 23:05:01 GMT

Gentlemen, looking for your assistance.

Current setup is 89 Trans Am with a T56. Did the ECM swap from a 165 > 730 ECM and converted to Speed Density.

My last reading I need is my VSS. This is the current setup, and I�ve tried a few different. The APP has given me a reading but tunerpro and my speedo are not capturing any reading.

IGNITION+ to Pink/Black Power @ Buffer Box
GROUND- to Black/White @ Buffer Box
SPD+ not used
INPUT to yellow from VSS
SPD- to purple from VSS and purple from buffer box closed.
OUT1 not used
OUT2 not used
OUT3 to yellow buffer box
OUT4 not used
OUT5 not used
SPd out to H-L and then set the "cal" to 1.181 (I have 3.73 gears).

Need some help getting my 86 camaro running

Brzagod21 — Fri, 15 May 2026 02:41:54 GMT

So recently i bought a 86 z28 Camaro 305 TPI with he auto tranny and Ive been stumped ever since i bought the car. bought it for a steal cause previous owner didnt want it taking space bought it for $1000 CAD and its in fair condition has little rust but nothing major but you know its a project. Quick rundown of the car its not perfect it didn't have a starter which i have bought waiting for delivery and other than that everything is intact. I hooked up a new battery made sure it was fully charged and no power was getting in so i thought maybe its a ground issue sanded down the grounds and made sure everything was snug but no power to the interior or the fuse box under the dash. previous owner seems to have tried to hook up a sound system and has spliced the wires underneath but im new to these cars and i dont wanna mess it up. Ive attached a photo of the bottom of the dash where all the wires are this is from the previous owners listing btw, i have the car stored nicely in a barn on 4 jack stands and i use it as my shop since im in the country side. i can take more precise photos if you guys need it im just hella stumped this is my first every muscle car which i bought because it looked cool and hell its a camaro. Any info or any help is much appreciated just want some help from the big leagues so 17 year old me can start this project and get her running

Battery not charging.

DigitalDan3 — Wed, 13 May 2026 22:49:23 GMT

Just replaced my Alternator on 1988 project car which sat for 19 years. Still not charging. Someone changed the battery cable ends to top post. There are 2 main wires coming off the positive post. One goes to the alternator the other the starter I believe. Off of the Alternator wire there are 2 more wires molded into the casing. One black and connects to red at the connector which goes to the fuel relay the other is orange which I have no clue where it goes. On a previous thread it was determined that there was a break in the black-red wire going to the fuel relay as this should have power all the time. I fixed that thanks to you guys the car runs! I took apart the connector on the orange wire and it has 12 volts so there's no break in the wire there.

One post said there was a Battery light on the dash and if it's blown out it would not complete the circuit or enough resistance to kick the alternator on. I tore apart the dash. No battery bulb. Ugh.

The plug going into the alternator has three wires (Red, Tan and Black) Red is hot all the time. Tan is Hot when ignition is on. Tan wire tells alternator to switch on I believe. Black wire ground? I am not sure why I am only getting 11.8 volts at the battery and car is only running off the battery.

I suspect that maybe the cable from the positive to alternator is bad. I did a continuity test and it's not an open line.

Any help would be much appreciated.