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Pulsating Interior Lights and Voltage Gauge With Turn Signals

5K views 26 replies 9 participants last post by  sleepyhollowtaman  
#1 · (Edited)
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.
 
#2 ·
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.
 
#4 ·
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.
 
#7 ·
Is the voltage regulator integral to the alternator in a 1979 Firebird, or is it a separate unit?
 
owns 1993 Pontiac Firebird Trans Am
#16 ·
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.
 
#17 ·
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.
 
#18 ·
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.
 
#22 ·
You haven't dropped a ground but here might be something to the corrosion theory, if so its going to be a PITA finding where that corrosion is. Probably in one of the blinker harnesses, but every ground point, connector, and socket in each harness needs gone over. The condition is very normal though and does not negatively impact anything. You can live with it, try and track it down, or maybe you can just slap an appropriately sized capacitor across the back of the gauge to even out the load and stabilize the needle.

I did say all of my GM vehicles did/do this and I consider it a "GM thing", but on further thought, every GM i've owned but one was at least 5 years old. My '96 Corvette which I said is the worst of the bunch does have some corroded grounds. The car is a grounding nightmare actually. The one GM vehicle I had from new might have done it but I don't recall.

At the endnof the day, it's down to how much it bothers you. If it's an OCD thing for you, definately try to resolve it. Otherwise, just let it be and move on to another project.
 
#25 ·
I don’t know, I’ve repaired electronics for 20+ years…..always started at the source. Verify power supply is correct and have proper voltages where they are supposed to be. Then move down the line….looking for bad wires, circuits, corrosion etc… you don’t just jump to the carb without knowing you have gas in the tank . Sorry if this sounds argumentative
 
#26 ·
Hey, Whatever method works for you is good. It may not be the best attack, but that doesn't matter if you get it fixed. I have known a lot of wild guys in the business that succeded against all odds ;-)