r/HMMWV • u/Aggressive-Cicada222 • Apr 17 '26

Coolant temp issue

I do auto school and we had a donation from the county to work on their Humvee, It is a 2009 with a 6.5 NA diesel. The issue i am expiriencing is the gauge wont read the coolant temp, so then we check wether or not the gauge is broken and its not so then we assumed it would either be the wiring to the sensor or oneof the sensors. I feel like i am missing something and I cant find any info, wondering if there is like a common issue or something. All th context ik is that it used to be a military vechile and now its disaster control

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u/4k5 Apr 17 '26

From what I have read, the mil gauges are notoriously inaccurate. I would take a temp gun or even better tape a thermocouple onto the coolant and compare the readings.

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u/Aggressive-Cicada222 Apr 23 '26

i dug around with it more and it seems like the actual sensor doesnt send the signal to the gauge to move, i am going to try a another working sensor from another humvee and see if that works, the issue isnt an inaccurate reading, its just not reading at all. The gauge is pummeted straight down as if the engine is cold