Luke42_02

I rebuilt the head in my XJ a while back and accidentally damaged the temp sensor at the back left of the head. I have tried 3 different replacement sensors and all I can get is a dead gage that sits at 0. When I ground the temp sensor wire, it pegs the gauge on the high end, so I do not think it is a gauge or wiring problem. Water flows out the hole when I remove the sensor, so the coolant appears to get there. I am totally out of ideas, can anyone help?

LACK

If you have a multimeter have you measured the resistance? Easy way to check to see if the sensor is functioning properly.

COOLANT TEMP SENSOR & MANIFOLD AIR TEMP SENSOR RESISTANCE TABLE
Temperature *F(*C) Minimum Ohms Maximum Ohms
-40 (-40) .............. 291,490 .......... 381,710
-4 (-20) ............... 85,850 ........... 108,390
14 (-10) ............... 49,250 ............ 61,430
32 (0) ................. 29,330 ............ 35,990
50 (10) ................ 17,990 ............ 21,810
68 (20) ................ 11,370 ............ 13,610
77 (25) ................. 9120 ............. 10,880
86 (30) ................. 7370 ............... 8750
104 (40) ................ 4900 ............... 5750
122 (50) ................ 3330 ............... 3880
140 (60) ................ 2310 ............... 2670
158 (70) ................ 1630 ............... 1870
176 (80) ................ 1170 ............... 1340
194 (90) ................. 860 ................ 970
212 (100) ................ 640 ................ 720
230 (110) ................ 480 ................ 540
248 (120) ................ 370 ................ 410

Luke42_02

Thank you so much, I think I have finally figured this one out!

When I went to the dealer to get the part, they told me that the Cherokee only has one temp sensor and that they had no record of the sensor on the rear left of the head. I ended up just looking through temp sensor pictures online until I found the match. It said it was correct for my vehicle so I bought #56026710AB. The part fit perfectly, but the plastic electrical fitting was black instead of white. I tried 3 different ones but none worked. Today, I found #56027012 which is the exact same sensor with a white cap (like the original). I now believe that 56026710AB is for some god-forsaken version of the Cherokee that does not have a temp gauge but only a warning light that kicks on when it gets too hot. As such, 56026710AB only flows current once it exceeds the temp at which the warning light should come on. I have ordered what I think is the correct part, (56027012) we will see if I am right.

Luke42_02

Wow, sure enough, the 1992 brochure lists an "instrument cluster" option package which adds a tach, voltmeter, oil pressure, and engine temp gauge as well as a low fuel indicator light, and trip odometer.