[BARRACUDA1968]

I have a 78 Y88 Trans Am and I installed a new battery and ground cable this spring.

Started the car and noticed my left turn indicator stays on all the time. It blinks fine but stays lit. All lights work on the exterior. My tach also quit working.

Second issue I noticed when I put it in the garage is the dash lights stay on when the car is off. I pulled the cluster and found the circuit board had some bad spots on it. Installed a new one still have the issue.

I tested the dash harness and the only wire that has power is the orange and black wire for the clock when the car is off. I can't figure out where the cluster is getting power to light up the dash lights?

So I installed a new headlight switch, still have the issue. If I dim the lights when the car is off the cluster will dim and when they go out the HVAC light comes on?

I checked ground to the dash and re secured it. Still have the issue.

Basically I have dash lights all the time. With the car off and headlight switch off the cluster lights up but no other gauge in the car does.

If I pull the light switch on I lose a few lights in the cluster but then the volt, gas gauge and HVAC lights come on. Just not very bright.

One other thing that I will mention is the first day I took it for a drive it ran fine, I went 60 to 70 miles cruising and stopped at a buddies house on the way home. When I left his place and turned on the highway it cut out like it lost electrical power or fuel. It was a very quick cut out so I doubt fuel related? It did this for a quarter mile or so then quit doing it.

I'm at a loss as to what to do now?

How are my gauge lights getting power when it's not coming through the dash harness?

Any suggestions would be great!

[2002Z4CSS]

Try running a ground right from the negative battery post to the dash frame and see if the problem goes away.

[BARRACUDA1968]

Ok I will give that a try.

Thanks

[BARRACUDA1968]

I ran a dedicated ground from the battery to the cluster. I touched the screw on the cluster that is supposed to have a linked ground to the light switch and got a spark.

Where do I go from here?

[2002Z4CSS]

Make up a good ground for that cluster. Ground it to the body.

[BARRACUDA1968]

Where should I hook the ground to on the cluster?

["QUICK-SILVER"]

Check the ground wire for the tail light harness. Usually bolted to floor pan of trunk underneath the mat. It could be off or just plain rotten.
On stick cars you can get feed back to the ignition switch, dash lighting, etc.....tach even quits working..

If this should be your problem you can ask me about the time I went to cut my car off and the engine wouldn't quit running. Stick car with factory reverse column lock. Brake light power feeding back through back-up light wires. And had the same dash problems this car is having.

[BARRACUDA1968]

Originally Posted by "QUICK-SILVER"

Check the ground wire for the tail light harness. Usually bolted to floor pan of trunk underneath the mat. It could be off or just plain rotten.
On stick cars you can get feed back to the ignition switch, dash lighting, etc.....tach even quits working..

If this should be your problem you can ask me about the time I went to cut my car off and the engine wouldn't quit running. Stick car with factory reverse column lock. Brake light power feeding back through back-up light wires. And had the same dash problems this car is having.

I'll check that tonight, I have a couple hours to work on the car. I did put a multi meter on the gauge cluster housing and I am reading 11.74 volts. That's with the key off.

I am also going to pull the cluster back out and remove the clock hot wire out of the harness and try again. That is the only wire that has power when the key is off. If that doesn't do it then it's backfeeding from somewhere else.

[BARRACUDA1968]

I checked the trunk for a main ground and I don't have one. I have a harness coming from the drivers side routing to all the taillights. I had one taillight out so I fixed that. There are 2 little grounds that are good. I do not have any light bulbs in the back up lights?

I pulled the cluster back out and my circuit board is burnt just like the old one.



I'm pointing to where the burnt circuit ends up on the harness which is the ground.

I pulled the hot clock wire out of the dash harness and that stopped the dash lights from coming on with the car off. Now I know why, the cluster is not grounding for some reason and that hot wire was feeding the metal housing I guess?

I followed the ground wire from the dash harness and it ends up in a bundle of taped wires. I haven't gone any further.

I hate to order a new circuit board and burn it up too. I didn't realize the first time when I plugged the harness in to the new circuit board that the dash needed to be all put back together to be grounded. Maybe that's how I burned up the new circuit board. Can I repair it somehow?

I hate taking up everyone's time on this because I don't have a lot of electrical knowledge so I ask dumb questions but I at a loss.

I tried to ground the dash cluster right from the battery and still get a spark so getting the dash cluster grounded at this point isn't my problem. I somehow have power coming from somewhere causing the metal dash harness to have voltage. Seems to me that is what's burning up my ground on the circuit board?

Anymore ideas?

["QUICK-SILVER"]

Tach/clock assembly just about has to be shorted out. Something in it letting too much current go to ground. More than the printed circuit could handle.

Being very careful you can solder a jumper wire across the break in the printed circuit. Heavy duty clear boxing tape works good to repair the plastic. Use a thin film of clear silicon on the solder joints. (This can be talked about more later)

For now I would remove the tach/clock assembly from the cluster and put everything else back together. You will need to add a ground wire to dash under the nut on the far end of the burnt circuit. That's if you don't repair where it's burnt first.

A short in that area would explain the engine running crazy when it did. Tach grounding coil wire out.

Power on that side of the cluster, shorted without proper ground, would also explain why left front turn was on. That power had to go somewhere. And like water it took first availbile exit.

Anyhow, get the tach out, fab a ground jumper, and mock fit everything back together. I suspect all your lighting woes will be cured.

Clay

[BARRACUDA1968]

Originally Posted by "QUICK-SILVER"

Tach/clock assembly just about has to be shorted out. Something in it letting too much current go to ground. More than the printed circuit could handle.

Being very careful you can solder a jumper wire across the break in the printed circuit. Heavy duty clear boxing tape works good to repair the plastic. Use a thin film of clear silicon on the solder joints. (This can be talked about more later)

For now I would remove the tach/clock assembly from the cluster and put everything else back together. You will need to add a ground wire to dash under the nut on the far end of the burnt circuit. That's if you don't repair where it's burnt first.

A short in that area would explain the engine running crazy when it did. Tach grounding coil wire out.

Power on that side of the cluster, shorted without proper ground, would also explain why left front turn was on. That power had to go somewhere. And like water it took first availbile exit.

Anyhow, get the tach out, fab a ground jumper, and mock fit everything back together. I suspect all your lighting woes will be cured.

Clay

That makes sense. I plan to repair the cluster today hopefully. I checked grounds last night with ohm meter using my ground jumper wire to the battery and cluster ground is good and so is the ground mated to the lower dash frame. I'm going to go through each wire on the dash harness using the dash harness ground and check voltage to each wire with the multi meter too. That way I know it's not in the harness and more likely in the cluster.

I'll pull the tach out and put it back together like you suggested. I couldn't figure out how the car cutting out like it did and this problem were connected but grounding through the tach make sense. I had kind of suspected maybe my coil was going bad?

I bought this car last year and just didn't mess with it much, just parked it and fixed a few fuel issues and power steering problems. The other issue I had last year after fixing the fuel problems, (new gas tank and sender; fuel pump; new fuel lines and filter) The car would run hard through first and half way through second fall on it's face until I let off the gas. It didn't seem to cut out like it did the other night meaning it wasn't as quick of a cut out but maybe it's related or it was the start of the problem I'm having now. The tach did work then but as of this spring the tach is DOA.

Thanks for the tip!

[BARRACUDA1968]

I made the jumper wire and fixed my circuit board.

I did an ohm test on the board and all is good.

I then did an ohm test from my harness ground to the dash ground and ground jumper from the battery. All good there.

Removed the tach and re installed cluster. I think it worked. My turn signal light went out and functions correctly now. All the dash lights than can light up do. Without the tach in there you can't plug in all the light sockets. Dash lights in the cluster are nice and bright too.

My oil gauge doesn't work now but that could be because the tach is out and not completing the circuit on the board?

Next question, how do I test the tach to see if it's fried? or shorting out?

BTW thanks "Quick-Silver"

["QUICK-SILVER"]

Tach and clock both, probe wires going in to ground with your ohm meter. A flash is all you should get on both of them, that's testing + terminal to ground (metal mounting flange or ground nut). The flash of numbers on your ohm meter will be a capacitor or such charging up. It wont do it again untill you disconnect and rehook. Tach + to coil - shouldn't show anything.
Just got the same results on two different, known good, guage pods. One out of a 79 TA and the other a 80 model out of that other brand F body.

Any solid or true reading you get from + to - would be something shorted out or a component not switching like it's suppose to. Pretty much making a short. That said, I can see where in testing things might look good and go bad when power is applied.

You can hard wire either of the guages straight to battery also. Fab a few jumper wires and run one wire to the tach terminal at the distributor. If you try this be careful not to get bit. Tach and clock both have capacitors that charge up and they do bite if you let them.

Clay

[BARRACUDA1968]

Thanks again, I will try some of this this afternoon. I can't start the car because I just took my carb to have it rebuilt but I can do everything else.

My tach may be good due to the fact that my new circuit board got damaged due to bad ground when I installed it.

I'll do the tests and report back.

[BARRACUDA1968]

I tested the tach and found no problems and I also got the clock to work on the bench.

I also worked on the cigarette lighter and got it working but no dice on the rear defrost?

Anyway I put the tach back in the cluster and put everything back together. All is good so far. I'm having my carb rebuilt right now so I can't start the car but nothing funky going on and all the dash lights work. Even the clock works!

The tach needle moves just a hair when I turn the key on so hopefully thats a good sign.

Thanks for all the help!