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Old 02-07-2024, 11:16 PM
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Default I thought I was pretty good at electrical, apparently I suck.

Backstory... got car painted, engine in and broke in, engine runs well, etc. I knew I would have to go through this car after painting, cleaning grounds and all that. Finally move into the car and nothing but problems. The guy that painted the car removed and reinstalled the dash, put it all back together the way he found it.. yeah right. I have no dash lights, turn signals inside, fuel gauge, amp gauge, oil pressure, water temp, I think the wiper motor works, but do have headlights, dome light works intermitantly, right turn signal flashes the fasten seat belt light and no courtesy lights work. The engine charges, starts, runs, etc. The gauge cluster is a 78 with a separate tach harness not plugged in yet. Is there a ground wire under there I missed? If so where? Car is an 81 TA. I'm kind of embarassed to post this but I been at it for a while now and don't want to be like those dudes that ask tire pressure on FB.

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Old 02-08-2024, 08:20 AM
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If you have as many gremlins as you're posting, you're going to need a good legible schematic that you can refer as you chase down each circuit. Lots easier than coming here to ask what color wire does what, then hoping you get correct information.

Even if the guy that removed, and reinstalled the dash didn't screw anything up, who knows what has taken place as the car has sat. Corrosion, rodents and accidentially breaking connections in old wiring are a distinct possibility. Now you're following up someone that may, or may not, have reinstalled everything correctly. Get the schematic before you go crazy trying to figure out the electrical engineering from 50 plus years ago. It's lots easier than trying to figure out what that wire does under the dash that is just hanging by itself.

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Old 02-08-2024, 09:37 AM
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I know nothing about auto electric. But have always been told (and read) to check the grounds first. The wiring schematics are a must but can be a bit confusing to read if youre not familiar with that kind of stuff. You didnt say what motor is in the car. If that has been changed as well sounds like you have mix of years going on. A schematic may not be all that helpful.

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Old 02-08-2024, 11:16 AM
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It is an 81 TA turbo. I removed all the turbo wiring 3 years ago, labeled things and removed things I was not using. At that point everything was a OK except the clock. Since then the car has been indoors climate controlled. I do have a schematic. The fact that the turn signal flashes the fasten seat belt light tells me at least one ground is bad. I just dont know where the ground is. Is there a screw in the firewall? Multiple issues have been squared away on the outside by cleaning overspray from ground locations and in light sockets. I really appriciate yu gys trying to help!

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Old 02-08-2024, 11:19 AM
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The car had a 400 when I bought it but was a turbe 301, I put another 400 in it. I put a 79 engine harness in it.

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  #6  
Old 02-08-2024, 12:11 PM
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Quote:
Originally Posted by 4dblnkldude View Post
It is an 81 TA turbo. I removed all the turbo wiring 3 years ago, labeled things and removed things I was not using. At that point everything was a OK except the clock. Since then the car has been indoors climate controlled. I do have a schematic. The fact that the turn signal flashes the fasten seat belt light tells me at least one ground is bad. I just dont know where the ground is. Is there a screw in the firewall? Multiple issues have been squared away on the outside by cleaning overspray from ground locations and in light sockets. I really appriciate yu gys trying to help!
Should be a ground from the pass side head to the firewall, braided copper wire. Big thick gauge wire from lower driver side trans to block bolt then to the floor. Thick wire from battery to head.

Inside should be ground wire in the harnes to driver/pass side bottom metal frame of dash. Also gauge cluster housing should have the metal strap between headlight switch screw to upper left housing screw. Tach has no ground wire, just power wire from fuse block terminal and other wire to tach on distributor.

Besides those ground locations, check all body light sockets/wires for good clean connections, I had a front parking light issue on one car that was the ground wire where it internally connected to the "strap" in the socket the light bulb touches, once that was cleaned & verified good connections it fixed the problem.

Clean all ground connection points of paint/rust, verify the other ground wires/straps are good & clean verify all light bulb sockets are good... & light bulbs, the little lead connection point on older bulbs can go flat and not make good connections. When a turn signal bulb/socket/wire is bad, the other side will usually blink faster to let you know theres a problem.

Wiring can be fun... good luck!

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Old 02-08-2024, 01:26 PM
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This is what Im doing tonight. I have those big ground locations and the strap betwen HLS and cluster. Its that ground under the left side I gotta look for. Thank you! Been looking at some old threads.

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Old 02-08-2024, 02:47 PM
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This may help you with the locations of the dash grounds. Also, I have an 80 diagram but no 81. I’m not familiar enough with those two years to know if there are any significant changes between them (I don’t think there are) but I could email you a copy if you’d like. Diagram isn’t in color unfortunately but still helpful. I’ve used my 77s countless times. The factory service manuals are wonderful.

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Old 02-08-2024, 03:23 PM
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I have no idea what your factory wiring should look like, but maybe you could easily test your theory about grounds before getting sucked into diagnostic diagram quicksand?

If you suspect it's a ground issue between the dash and the chassis, would you be comfortable just running a long wire between the negative terminal of the battery and an obvious ground point on the back of your dash? This might be a quick way to test your hypothesis about grounds being the problem.

For example, you could ground just one dash light and see if that fixes it. If it does, then you can continue chasing factory grounds with a little more confidence. If not, then you might have to step up to wading through wiring diagrams for missing power connections or shorts.

I agree this stuff is painful and the factory diagrams are not easy to interpret the first few times. I've had to use both wiring diagrams AND assembly diagrams to figure stuff out and it took a lot of time. Good luck and I hope it turns out to be something simple.

Mike

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Old 02-08-2024, 03:28 PM
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Each side of the headlight harness has a ground to the core support. Fuel gauge grounds in the trunk. Is your oil pressure hooked up at the motor end? There is no specific ground to that, I suppose its grounded through the dash someplace.

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Old 02-08-2024, 10:31 PM
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Quote:
Originally Posted by bhill86 View Post
This may help you with the locations of the dash grounds. Also, I have an 80 diagram but no 81. Iím not familiar enough with those two years to know if there are any significant changes between them (I donít think there are) but I could email you a copy if youíd like. Diagram isnít in color unfortunately but still helpful. Iíve used my 77s countless times. The factory service manuals are wonderful.
I think the 80 and 81 are pretty different. Also it was a turbo car, but they had them in 80. LOL.

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Old 02-08-2024, 10:36 PM
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I did find a ground right out of the harness taped up in body shop tape. I grounded it and the wiper motor works. Just font know where it screws too. I only had an hour tonight and wont be able to do anything until next week. Thanks so much for all the ideas!

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  #13  
Old 02-09-2024, 02:54 PM
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You don't need the Turbo wiring on an 81 for everything else to work. My already had the the turbo and computer wiring taken out.

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Old 02-11-2024, 11:11 PM
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Quote:
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You don't need the Turbo wiring on an 81 for everything else to work. My already had the the turbo and computer wiring taken out.
Correct! I removed everything in the engine compartment. Tomorrow I'll have a few hours to hit it again.

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Old 02-12-2024, 10:32 AM
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The 81 Temp sensor for the gauges uses a different ohm range than earlier ones do.

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  #16  
Old 02-12-2024, 10:50 PM
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There was a good dash removal tutorial on hitmans site (78ta.com). This tutorial had some good pics/info on wiring. I think this was the link, https://www.78ta.com/old/rdash.php
But, just tried the link now and it appears hitman's site is down ? gone ?

As 78w72 says there is a small metal strap between the gauge cluster housing (upper left housing screw on gauges) and the headlight switch screw. It could be easy to miss that small metal strap. So, make sure that small metal strap / ground is there and it is good. I also ran a separate wire from there directly to the metal core of the dash.

Hoghead's Firebird and Trans Am Parts has some good dash wiring pics too, see
https://firebirdtransamparts.com/tec...ss/harness.htm


Last edited by pippintook; 02-12-2024 at 11:00 PM.
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Old 02-13-2024, 03:15 PM
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Quote:
Originally Posted by Skip Fix View Post
The 81 Temp sensor for the gauges uses a different ohm range than earlier ones do.
Do you know what one? I had that problem too.

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Old 02-13-2024, 03:28 PM
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OK, heres where I am. The green wire from the headlight switch goes down to the fuse panel with a 5 anp fuse and powers the gray wire courtesy circuit. Dirty HL switch connections caused that. I have dash lights, I'm gonna run a separate ground from the cluster to somewhere. Now the high beam indicator light is on all the time but the lights work fine. I just read somewhere on here there is another ground on the other side of the dash that connects to the dash frame, I'm gonna look for that later tonight. I also found a single element in the back where a double should be, every taiillght was nice with alot of wire except the middle drivers side, It seems like less wire. Does not look previously repaired though. Then I'll move onto the pass power window, I think that is just in the switch. I'll tell ya I got like 25 hours into this but learned a hell of alot!! It would have been way easier if it was just popping fuses. LOL Thanks for all your responses and keep em coming especially why that pesky high beam light is on!

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Old 02-13-2024, 11:26 PM
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More work tonight, focusing on the cluster. In 81 there is a clock in the cluster but what wire powers it in the harmonica? The 77 cluster I'm using has a clock and the orange wire powers it.

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  #20  
Old 02-14-2024, 07:49 AM
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It's an orange wire but doesn't go to harmonica. Looks like it eventually goes to ignition switch. It branches off a cluster of orange wires.
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