[Red_79_TransAm]

We are working on completing a full restoration and when I turn on the turn signals, the interior lights and the voltage gauge pulsate. In addition, they dim when pressing the brakes. I have tried it with the car running as well and the same results. Here is what I have tried so far:

1. New Battery was installed recently and is fully charged
2. New Alternator was installed recently
3. New headlight switch
4. New printed circuit board on back of instrument cluster
5. Scraped off the paint to make sure my grounds have good connections
6. Unhooked the hardness for the taillights, turned on hazards and same results which leads me to believe it’s not in the rear lights.
7. Verified the following grounds:
   1. Right and Lift side headlight grounds coming out of harness to core support
   2. Ground from battery to the front of the block
   3. Ground from the back of the engine to the firewall
   4. Ground from the transmission to the frame
   5. Ground connected to the dash from the instrument cluster
   6. Ground from the rear lighting harness

Is there somewhere that I could hook up an additional ground to verify if it is a grounding issue or to solve the issue?

Thanks for the suggestions as this one is really starting to frustrate me. I don't want to put the rest of the stuff in the dash and interior until this is resolved.

 

[myk74]

I'd try (with jumper cables at least) a ground from the battery to the frame.. I know the ground from the tranny to the frame should be just fine, might also try a ground from the battery to the firewall. Sure sounds like something isn't grounded or grounded good, hard to say exactly what.

 

[bcola]

Do the lights pulsate in time with the turn signal flashing? Or what kind of pulsating?

 

[GaryDoug]

Thanks for the suggestions as this one is really starting to frustrate me. I don't want to put the rest of the stuff in the dash and interior until this is resolved.

Do you have a multrimeter and know how to use it (easy)? Use the wiring diagram to probe the voltage shown on the meter while the problem exists. The best troubleshooting technique is to start at the middle of the current path and move up or down as the tests results dictate....narrow it down.

 

[Red_79_TransAm]

Do the lights pulsate in time with the turn signal flashing? Or what kind of pulsating?

They pulsate in time with the turn signal flashing and pressing the brakes. When the signal illuminates or the brakes are pressed, the lights inside dim and when they are not lit, the lights inside brighten.

 

[Red_79_TransAm]

Do you have a multrimeter and know how to use it (easy)? Use the wiring diagram to probe the voltage shown on the meter while the problem exists. The best troubleshooting technique is to start at the middle of the current path and move up or down as the tests results dictate....narrow it down.

Yes, I have a multimeter and can work my way around it but could you explain a little more as to where I would test voltage and what I would be testing for? Thanks!

 

[1993TransAm]

Is the voltage regulator integral to the alternator in a 1979 Firebird, or is it a separate unit?

 

[Red_79_TransAm]

I'd try (with jumper cables at least) a ground from the battery to the frame.. I know the ground from the tranny to the frame should be just fine, might also try a ground from the battery to the firewall. Sure sounds like something isn't grounded or grounded good, hard to say exactly what.

I tried jumper cables to the frame, firewall, core support and even ran it inside of the vehicle and same results.

 

[Red_79_TransAm]

Is the voltage regulator integral to the alternator in a 1979 Firebird, or is it a separate unit?

From what I can tell online, it is integrated into the alternator.

 

[myk74]

Well, to determine if it's a ground issue or a 12v+ issue, run a ground from the battery to the ground on the interior light and see if it does it under the same circumstances

 

[b_hill_86]

Could you try posting a video of the pulsing?

 

[Red_79_TransAm]

Well, to determine if it's a ground issue or a 12v+ issue, run a ground from the battery to the ground on the interior light and see if it does it under the same circumstances

I ran a ground from the negative on the battery to the metal where the ground for the interior hooks up and still have the same issue. I’m going to post a video with what it’s doing and what the multimeter reads on each fuse.

 

[Red_79_TransAm]

Could you try posting a video of the pulsing?

Here is a video of the pulsating in the lights, the voltage gauge and what my multimeter is reading. I tried my multimeter on each fuse and it did the same for all of them.

Lights.mov

drive.google.com

 

[EdKnecht]

Ok, lights pulse when turn sig is on and dim more when brakes are applied ? Do they dim with out the turn sig on when pressing the brake ? Did you pull the flasher unit and try manually flipping the signal to see if it pulses ? Crappy flasher ?

 

[Red_79_TransAm]

Ok, lights pulse when turn sig is on and dim more when brakes are applied ? Do they dim with out the turn sig on when pressing the brake ? Did you pull the flasher unit and try manually flipping the signal to see if it pulses ? Crappy flasher ?

Correct, they pulse with signal on and dim when brakes are applied. Yes, they dim without the turn signal on and when the brakes are applied. I have not tried pulling the flasher but the same issue occurs with the hazards on as well as the signals and they are on different flashers.

 

[b_hill_86]

My 77 does the same with regard to the pulsing gauge. Never paid attention to the dome at the same time. I’ll check when I can. But light’s definitely dim slightly when brake is pressed also. I always attributed it to higher draw and not being a problem per se. I believe this is normal.

 

[ZumpTA]

My 77 does the same with regard to the pulsing gauge. ... light’s definitely dim slightly when brake is pressed also. I always attributed it to higher draw and not being a problem per se. I believe this is normal.

Agreed. I didn't see anything in the video that looked out of the ordinary with the lights, but cameras and refresh rates can lie in that respect. The movement of the volt-meter is normal to me too. Every GM vehicle I've owned does/did this. Pretty sure my '80 Camaro did it, my 4th Gen swings a bit more than that even, and my C4 bounces a lot. I've always thought of it as a "GM thing" to be honest.

 

[EdKnecht]

I’ve had a lot of cars over the years and never had lights or gauges pulsate. I’d start looking at the positive cables. Dirt/ corrosion ads impedance to the equation so every time the load increases you get a voltage drop. The video shows …what… about a half a volt drop ? Not a deal breaker but sensitive electronics don’t particularly like voltage swings.

 

[GaryDoug]

Here is a video of the pulsating in the lights, the voltage gauge and what my multimeter is reading. I tried my multimeter on each fuse and it did the same for all of them.

Lights.mov

drive.google.com

Nothing unusual about that video. My 98, meticulously maintained by moi, has a similar fluctuation. I even hear slight IAC idle rpm waver synced with the turn signals flashing at a stop light. These are not factory new cars. They do have some weaknesses. Enjoy them.

 

[sleepyhollowtaman]

Do you have a multrimeter and know how to use it (easy)? Use the wiring diagram to probe the voltage shown on the meter while the problem exists. The best troubleshooting technique is to start at the middle of the current path and move up or down as the tests results dictate....narrow it down.

I would never start in the middle of a circuit. First I would verify I had a signal at the output. Next I would go to then end and see were the signal is corrupted. This case I would start pulling fuses and see when the problem stops. It sound like you have a ground issue somewhere. I would have your alternator checked. Voltage regulator bad? Try another alternator you know works. See if that changes anything.