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Rather than creating a brand new temp gauge topic I'm hoping to get an answer on my own gauge issue. Below is a picture of my gauge with the engine at operating temp (upper radiator hose was hot). Just replaced my temp sender today and got no improvement. However, it was a STANDARD #TS-268 rather than the Mopar part indicated way above this thread. Here's some testing that I just did:

 

• Grounded Sending Unit wire and the gauge pegged all the way to the right (key ON)

• Disconnected the ground from the sending unit wire and the needle went full cold

• 11.9V gets to the sending unit connector

With engine back at operating temp I measured resistance with CTS disconnected... got 165 ohm with the needle at this position:

• Needle never goes above this 110° mark

 

IMG_0100.jpg.baa9a763e5ccd443ea9168630d6ac43c.jpg

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2 hours ago, Ωhm said:

That looks more like the 200° mark. My guess is your reading 195°.

Ok, I see. Got that 110 by dividing 220 in half. I had a blind eye and didn't actually read the hotter numbers and their corresponding marks. :doh:

 

Anyway Ωhm, this gauge suddenly worked differently after my "Intermittent Turn Signal" thread. You helped me out during that which involved removing the instrument cluster.

 

Before that project it commonly read around the 220° mark. Now it won't go above 195° in the picture... except when shutting the engine off, and then it creeps up +1 mark.

 

Surely the engine is running hotter than this? This seems way too cool.

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do this:

 

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 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.

IP ground location

**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.**

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10 hours ago, cruiser54 said:

do this:

 

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 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.

IP ground location

**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.**

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I just added this ground jumper this past week. I used the stud that holds the E-brake assembly in place. Is this the correct spot? I can get a pic later for reference. 

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On 10/20/2022 at 4:39 PM, Ωhm said:

My guess is your reading 195°.

 

There may not be a problem with accurate reading after all. Today I reinforced the ground, using the 8mm stud by the parking brake. Testing with a multimeter before and after gave the same results on both grounds. Continuity read 3.7 at the lowest.

 

A friend thought I might have a 195° thermostat installed without my knowledge. He might be right because I've only owned my MJ for 1 year.

 

After driving around I used an IR thermometer. The upper radiator hose was 183° and the thermostat housing was 193°. Temp gauge showed the same results with it reading about 195°

 

IMPROVED GROUND

IMG_0111.jpg.b3bf591e30ff05a99525550f0cf4709b.jpg

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On 10/29/2022 at 10:50 AM, cruiser54 said:

Great, and expected. 

How are your gauges working? differently at all?

The only issue I had after going full cluster was the temp sensor/temp sender issue. My speedo needle is bouncing around but that was happening with the dummy cluster too. I’m pretty sure my cable is trashed. Pulled the clip on the frame rail to give me enough slack to get the old cluster out. As I pulled up the slack in the engine bay I noticed a large section of the hard plastic coating was gone and what looked like braid to me was exposed. I have a parts 89 that I’m going to pull the speedo cable off of to see if the one I have now is in fact defective. Only other issue I’m having is the cluster lights dim when I press the brake. That was happening before I added the ground jumper and it’s still happening. Did some searching online and found a thread about checking for bad connections on trailer wiring. This did have some hacked up trailer wiring spliced into the boom past the rear axle when I got it. I cut all the leads out but never opened up the loom did see what was done. I’ve been busy enough chasing down all kinds of other things, lol. 

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