86 gt 4 speed.

When i turn my day runners or headlights on my gauges(volt/oil) flat line. Turn the lights off and they fire right back up.

Any idea where I should start looking for a bad ground?

quote Originally posted by sirtimeless: 86 gt 4 speed. When i turn my day runners or headlights on my gauges(volt/oil) flat line. Turn the lights off and they fire right back up. Any idea where I should start looking for a bad ground?

I really wish I could be of more help, but there are a LOT of grounds INSIDE the car. In particular, under the dash I think there's got to be thfour or five ground locations... one on the passenger side, two in the center of the dash (accessible from under the dash). I think there's one in the shifter area, and a few by where the fuse block and power distribution blocks are next to the drivers left foot.

In the front compartment... the 87 has a relay that's attached to the frame (which is accessible when the wheel liner is removed). There's a ground there that comes from the headlight harness. Now... I've never had this issue in an 84-86, nor have I gotten around to restoring one... so I don't know if the ground is still there.

But there's got to be something getting shorted there...

I almost wonder if something is getting messed up on the printed plastic sheet that goes behind the gauges that all the lights twist into.

Do you have a seperate set of gauges? it might be worth it for you to remove the ones you have, stick in a spare set... and then see if you get the same result.

Thanks for the attempt I know this car has oodles of grounds. Was just curious if there was a localized one with the gauges and the lights.

I do not have a spare set of gauges. I can pop them out and double check everything there.

Weirdest part about it... I drove the car 6 miles that morning with my lights on, and everything worked. Parked it and took the truck up to green bay all day. Came home, turned them back on and the gauges spazzed. It did nothing but sit there for 10 hours haha.

G201 seems to be the only commonality in the different circuits. Maybe start by checking that ground. The thing is, that ground point serves a lot of circuits so I would think you would be seeing other problems but it never hurts to check the obvious. I would unplug the aux gauges and test the ground at cavity 4 (black wire).

Here are a couple pics of the circuit and ground location. They're from an 87 manual ( don't have the 86) but should be the same.

[This message has been edited by seajai (edited 09-06-2012).]

I will have to try and find that ground Thanks for the picture though. Should hopefully help a lot.

There are three plugs where wires connect to the instrument cluster. I was having problems with a number of lights out in the cluster on my 85GT and intermittent lights/gauges when various things were turned on. I reseated the three plugs and the problem went away.

It's worth a try.