Nick-B

My '90 XJ always had a low reading voltmeter that so many of us are plagued with. I had read of the fixes involving running a separate wire from the battery or replacing the resistor on the gauge to correct the low reading and figured "one of these days" I'll fix it.

Well, about a month ago the gauge died. Just pegged at the low end so I finally decided to "fix it".

After pulling the gauge cluster out I went to remove the voltmeter and noticed the screws that hold it in place as well as providing the electrical connection weren't very tight. I also noticed that all the copper contact surfaces were very dull and probably making extra resistance to each gauge and light socket. I pulled all the bulbs and contacting screws and cleaned up all the contact surfaces with some fine emery paper. Put it all back together and BINGO! Not only did the voltmeter come back to life but it now reads the correct voltage. No running an extra wire or replacing resistors.

Kinda goes along with Cruiser54's repeated mantra of cleaning all the sockets and relays in the engine compartment. Guess we can add the dash cluster circuit contacts to that "must-do" list as well.

cruiser54

Good find!!

This helps also, and I didn't come up with it myself. It helps also:

Improving the Instrument Panel Ground
The ground point for the complete instrument cluster on your XJ or MJ is located up under the driver’s side dash. If you lay on your back and look up under there with a flashlight, without wearing a hat, you will see a black wire attached to a shiny piece of metal almost directly above the hood release ****. The screw will have either a ¼" or 5/16" head on it.
This ground point is responsible for handling the ground circuit for the following items: Dome lamps, Seatbelt and key warning, trans comfort switch, wiper switch, headlamp switch and delay module, fog lamp switch, cargo lamp switch, all instrument panel grounds and illumination, power windows and door locks, cruise control dump valve, and a few more things.
The problem is that where the ground point is located does not have a good contact with the chassis where the ground should be. The solution is simple.
Make up a jumper wire with #10 gauge wire about 10" long. On one end, crimp on a ¼" round wire terminal. On the other end, crimp on a 3/8" round wire terminal.
Remove the screw from the existing ground wire and attach the small terminal of your jumper so that the original wire and your new jumper share the same attaching point, one over the other.
Look above the driver’s side plastic kick panel just forward of the top of the hood release ****. You will see an 8mm stud there. Attach the large terminal end there with a washer and nut over it tightened securely.
**Special note for Comanche owners: Make your jumper wire 12" long and attach it on the driver’s side kick panel close to the fusebox on the 8mm stud.**
　
Revised 11-29-2011

Nick-B

Yeah, I added that extra ground wire a while back hoping it would help the low voltmeter reading. No change on that but it is easy to do and definitely improves the marginal grounding system to the dash area.

cruiser54

Seems to help with the dash lighting also. I like your fix on the printed circuit "board".