Erratic volt meter...

[Whitewagon]

1989 GW. Pretty clean and a great runner......
Problem: When using the turn signals, left and right, The volt meter dances downwards and in time with the signal.
Battery is new, connections are clean. Alt is putting out 14.7 consistently even when the volt meter gets erratic.
This only occurs when the turn signals are used. Volt meter is not affected when turning on lights, fan, or any other
accessories, windows, power locks, ext, ext.
Does anyone know what is happening and what is the fix?
Is there a schematic on the ground locations for this vehicle?
I am not really good at diagnosing electrical.
I could clean up the grounds if I knew where they were.
I did replace the big ground from the motor to frame when I rebuilt the motor.
Thanks for reading..... Tim.

[Jenga77]

I have the exact same thing on mine, and I've completely replaced my harness with a Painless Performance universal fit. So I don't think it's down to faulty wiring, but could be a bad ground.

It's been a while since I did my wiring, so I don't remember all the details. But, (and I'm wildly speculating here) it could have to do with the "railway crossing" wiring for the front side markers and park lights. Because of that those front lights don't have a conventional ground, and instead intermittently ground out through one of the feed lines. It could be that is confusing the voltmeter by changing its reference. At least on mine the voltmeter is in the instrument cluster and shares a ground with the turn signal indicator lights, so there could be some cross talk or something. It's a modern voltmeter I put in the cluster, so it's probably more sensitive than the stock unit. You could try pulling the front turn signal lights or changing the voltmeter ground location and see if the problem goes away.

Another weird thing I have is when I turn on my headlights all the stock gauges rise by about 30%. Not idea what's causing this since the voltage regulator in the cluster shouldn't be affected by other circuits. Some day I'll have to dig into it, but by now I've kind of gotten used to it!

[devildog80]

Not the same issue but my '84 GW turn signal feeds through the headlight switch, and the ground is tied through the floor dimmer switch.
Working to track down why my front blinkers will not work when headlights are on (fender blinkers work all the time), with a friend having the same issue on his '80 CJ7, and not resolved until he added actual ground wires into his headlight/turn signal wiring directly from the lights to battery grounding.
I think we are all on the right track with our respective issues, that grounding is the key.

[Whitewagon]

Okay, all good info. Will check out the grounds up front. Thanks.

[nograin]

1984-5 Turn signals are powered through the flasher unit, which in turn gets power from a fuse on the buss which is switched on in run and accessory.
See section 24 of the wiring diagram. It's on the ol jeep Website. The diagram has an error on the tail lights which I corrected and sent to BJ's. Green wire is turn, Pink is stop, and white is marker and tail lamp.

1989. Alternator constant, and dash meter fluctuating. Look for where there may be a loose or poor connection between the alt output stud and the where the inside meter is sensing voltage.

[nograin]

1984-5 Turn signals are powered through the flasher unit, which in turn gets power from a fuse on the buss which is switched on in run and accessory.
See section 24 of the wiring diagram. It's on the ol jeep Website. The diagram has an error on the tail lights which I corrected and sent to BJ's. Green wire is turn, Pink is stop, and white is marker and tail lamp.

1989. Alternator constant, and dash meter fluctuating. Look for where there may be a loose or poor connection between the alt output stud and the where the inside meter is sensing voltage.