My temperature and oil pressure gauges reed too high!

[Glenn Bint]

So, as per title, anyone else come across this issue. Did you manage to repair?

[eaglescout526]

Have you recently swapped clusters from lights to gauges? Cleaned your grounds too?

[Eagle]

How high do they read, and how do you know they read high?

 

Does the oil pressure  change when the engine RPMs change?

[cruiser54]

Here's something you all should do at some point.

 

CRUISER'S MOSTLY RENIX TIPS

IMPROVING THE INSTRUMENT PANEL GROUND

NOVEMBER 17, 2015 SALAD 27 COMMENTS

 

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 knob. 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 knob. 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.**

[Glenn Bint]

On 6/12/2023 at 1:59 PM, Eagle said:

How high do they read, and how do you know they read high?

 

Does the oil pressure  change when the engine RPMs change?

Oil gauge is almost pinned at first start and drops about 25% when hot. Temperature gauge only goes up about 1/4 even with new 190 thermostat 

[pizzaman09]

13 minutes ago, Glenn Bint said:

Oil gauge is almost pinned at first start and drops about 25% when hot. Temperature gauge only goes up about 1/4 even with new 190 thermostat 

Your oil pressure is exactly like mine.  When driving it sits at 75% but idle is at 25% and cold start it is pinned at 100%

[Glenn Bint]

No it drops only 25% at idle. Basically reading 3/4 up

[PIKE]

On 6/11/2023 at 3:23 PM, Glenn Bint said:

So, as per title, anyone else come across this issue. Did you manage to repair?

 

Yes, by using an OEM Mopar sending unit.  Had the big fat aftermarket one and had the same results you are.

 

This is for oil pressure, not sure about temp.

[Glenn Bint]

3 hours ago, PIKE said:

 

Yes, by using an OEM Mopar sending unit.  Had the big fat aftermarket one and had the same results you are.

 

This is for oil pressure, not sure about temp.

Awesome 

[Eagle]

Neither the oil pressure gauge nor the temperature gauge reads in percent. The oil pressure gauge reads in psi, and the scale is linear. The temperature gauge reads in degrees, and the scale is NOT linear -- it's logarithmic. Telling us the gauges read 'X' percent is meaningless.