Fuel Gauge, Battery Gauge, Oil Pressure Gauge, and Temp. Gauge go dead when I turn my headlights on??? Turn lights off they go back on. This is a 1980 L82. Any one who can help would be appreciated. Also fuse that has power locks, power antenea, int. lights, and horn keeps blowing. Prior to blowing, antenea and lights work. Any suggestions where to start? Thanks:

 

Sounds like 2 problems, coincidental. Pull the center dash out and look at your connector on the back, check the ground and hot connection on the panel.
For the fuse thing, there can be several culprits. Look for an orange timer behind the pass dash, its for the ctsy lights. Also look closely at the cigar lighter, they tend to short againse the floor pan.

 

I had this exact same problem about 15 years ago with a 79 that was a burned car. When I would turn on the headlamps all the center gauges would go dead. Turn off the headlamps and the gauges worked fine!

The car had an engine fire and to cut to the chase… The problem was that the ground for the headlamp switch was corroded and not making good contact. As a result and due to the size of the power wire to the headlamp circuit, the car was seeking its own ground. The best one was to back feed and take out the center gauge cluster.

You have a ground issue somewhere in the car. It might be related to the other issue you have with the antenna and the fuse but there is no way to tell without pulling the dash out of the car and checking the wires.

Once I corrected my ground issue’s with the car, the headlamps and gauges worked just fine.

My suggestion would be to purchase a wire diagram for the car and start chasing grounds.

On the 1978-1982 cars, from the headlamp switch there is a 12 gauge black ground wire. I would first start with this wire and verify that you have a good ground. To do this, you will need to pull the center dash cluster from the car and access the headlamp switch connector. If you have a known source for 12V, attach your test light to this source and probe the 12 gauge ground. If you don’t light up, then start with this ground wire.

This ground runs in to the main dash harness and grounds multiple items in the car.

This ground circuit controls everything form the headlamps, the printed circuit on the center cluster, the anti theft alarm relay, The a/c hi blower relay ground, the seat belt warning buckle switch, and I believe the glove box lamp, and the lighter.…. It runs from the headlamp switch connector and then splits in to a giant branch inside the main dash wire harness.


Willcox

 

I removed the pop-up lights during a rewire of the car with a painless kit. I grounded my lights on the forward-most section, were the bumper and grill bolts to which was all removed later for body work (it's a 72). I had done the wiring before I removed the bumper/grill, so all worked fine while testing, installing. Later during interior reinstallation, front parts still removed, I discovered, smilier problems as you are having. The lights need a good ground and the ground buss bar I installed for my after market gauges and switch panel was it's prefered line. Having removed the center bumper support and headlight assembley issolated the grounds from the rest of the car. I know it's obviously not like your set-up but shows how interconnected things can get and hopefully point you in the right direction.

 

You are correct, and the headlamp circuit is so strong that if not grounded properly it will seek one! Thus knocking out other parts of the car.

 

Yeah, it was quite amusing, I messed around with it while diagnosing/working on it (I didn't at first realize the header bar I was using for ground was only attached to the frame through the removed items) I had the head lights blinking in reverse unisin with the turn signal indicators as long as the parking/gauge lights were off. neighbors probably thought I was nuts.

 

Nice description Willcox but a few followup questions

The headlamp switch is located to the left of the tach/speedo cluster yet we remove the center cluster. Does the ground from the headlamp wire back to the center cluster and therefore we are following that lead?

The way you describe, it sounds like the ground comes in from engine compartment harness, terminates at the center cluster printed circuit board and than routes to the headlamp switch.

 

80vette - click here for some wiring diagrams and other good '80 stuff...

 

I did this from memory, but it’s easy to verify the ground at the headlamp switch.

Find a wire with 12 volts on it, and then use this as the positive side (clip end) of your test light. Once you know you have 12v. on a wire, probe the black wire in the connector for ground.

I don’t have a wire schematic for your car here, so I’m not much help on where the final ground ends. But all the grounds mentioned come together in the main engine wire harness. They will be taped up and in the bulk of the harness!

I do have a 78 schematic here, and it shows a 12 gauge wire running from the same bulk branch of grounds and is marked Instrument Panel harness ground. I would assume this ground is going to the main cage of the car behind the dash pad or to the main door jamb area behind the kick panel on the driver side. I don’t have the right schematic or book here to verify it.

If you verify your ground on the headlamp switch it will probably be dead. But even if it’s not, this still can leave open the back feed possibility. In other words, you can get a false positive, but this should only happen with the headlamp switch in the on position with a draw.

I do have a 1979 assembly manual here, and it shows the main harness ground going the left hand side of the kick panel cage. You should be able to remove the kick panel and see a large 12 gauge wire with an eyelet on it. I would think that most 1978-1982 cars grounded at this point.

Willcox.

 

Thanks all! at least I now have a starting point. Very Much appreciated!!!

 

Could not bring up the electrical schematics. All other info I could get.
I don't know if you can fix this?? Thank you

 

Hate to say it, but call sales on Monday at 800-588-3883, we have these in stock. I'm with you, I could not get the link to work either and I don't have a scan of this on my laptop.

Willcox

 

I wonder if I might have a loose ground somewhere...I hooked up my headlights with some light bulbs I found in the back of the car and when my headlights are off the turn signals work fine...but flip on the headlights and the driverside blinks at a rate of on blink every minute to minute and a half and when blinking it just stays there til the minute or so is up and then it's wait. The other side works just fine. Could this be a ground issue too, or maybe a bulb thing.

thanks

 

I think all you need a pdf reader