Well, I finally got a scanner that can communicate with my Jeep.

The bad news - the scanner tells me my instrument cluster is giving wrong readings for RPMs and temperature.

The good news - the Jeep idles fine at about 750 (instead of what the cluster needle says around 1000 to 1200). And the temperature is also normal, even though the gauge reads high, to the right of the 210 mark.

All this time I was chasing those issues and it was the instrument cluster lying to me

I swapped out my old dummy cluster my years ago for this one with all the gauges that I have now. I will probably leave it alone for now, but hell, it never occurred to me it was that.

 

yeah... sometimes you got to take gauges that are mass produced from the lowest bidder with a giant grain of salt. Quality tools designed to give specific readings will almost always be better than what you see on a factory gauge cluster. They are more like "ball-park" readings IMHO for the most part.

 

ever done this?CRUISER'S MOSTLY RENIX TIPS

IMPROVING THE INSTRUMENT PANEL GROUND

NOVEMBER 17, 2015 SALAD 22 COMMENTS EDIT

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, seat belt and key warnings, transmission power/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 share 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. Use a coating of OxGard at all ground contact surfaces when attaching the screw and nut.

**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.**

 

Thank you, Cruiser, I will try this.

 

can't hurt and can only help.