Oil and volt meter gauges don't work when headlights on

Hi, I have a 1992 Jeep YJ with a 4.0 liter 6 cylinder and a 5 speed manual. My gauges all work fine until I turn on the headlights. When I turn on the headlights, the oil pressure and voltmeter gauges go to zero and the illumination for those gauges does not come on either. The other gauges (speedo, tach , temperature & fuel) are illuminated and working fine when the headlight switch is turned on.

What might be causing this? When I turn on the headlight switch, I hear a relay actuating behind the dash. What is that relay and what does it do?

Thanks in advance for your help,
Bob

Thanks Gilaguy23. I will give it a try and report back.

It puzzles me that everything works fine until the headlights are turned on -- then the 2 far right-hand gauges got to zero. Almost like the power and/or the ground to those 2 gauges is disconnected. I guess it could be a current draw issue.

When I turn the headlights on and off, I hear a relay cycling on and off behind the dash near the gauges or glove box. What is that relay and what does it do?

Bob

bobcreag said:

Hi, I have a 1992 Jeep YJ with a 4.0 liter 6 cylinder and a 5 speed manual. My gauges all work fine until I turn on the headlights. When I turn on the headlights, the oil pressure and voltmeter gauges go to zero and the illumination for those gauges does not come on either. The other gauges (speedo, tach , temperature & fuel) are illuminated and working fine when the headlight switch is turned on.

What might be causing this? When I turn on the headlight switch, I hear a relay actuating behind the dash. What is that relay and what does it do?

Thanks in advance for your help,
Bob

Click to expand...

So there's a 13-pin connector that connects the wiring harness behind the dash to back side of the gauge cluster (4WD indicator, fuel, temp, oil and volt meter gauges). All gauges would work fine with headlights off. As soon as I turned on the park lights or the headlights, the oil and volt meters would turn off and the illumination for those gauges did not turn on. It turned out that I had a poor connection between the male and female pin connector for the gauge panel. When I removed the ground and positive wires from the connector, sprung them out slightly, and re-inserted them into the connector, everything worked!

Prior to this, I checked fuses, cleaned engine and chassis grounds, re-soldered the connector pins to the cluster printed circuit board -- all to no avail.

Before the fix, I found that I was getting full battery voltage at the illumination light bulbs and at the 2 gauges. But when I attached an external 12-volt tail light bulb to the printed circuit board where the normal dash illumination bulbs attached, the light would not turn on. It seemed that I had full battery voltage, but not adequate current flow.

I could not have solved this problem without the wiring diagrams supplied by this website. Thank you so much! The problem was with Black wire connected to pin No. 1 which goes to ground splice Z1,3, interior lamp illumination circuit. The gauges on the right side share this ground.