Hi, ever since I bought my truck the temp gauge doesn't work properly. The needle just slowly fluctuates up and down in low temperatures even though the coolant is hot . I checked the temperature sensor, wiring from the sensor to instrument cluster and the instrument cluster PCB. But everything seems to be all right. I heaven't checked the instrument cluster ground wire, but I assume if it was broken, the other gauges wouldn't work too. So the last thing that comes to my mind is the temp gauge itself is broken. But before I'll try to disassemble the gauge I am here.
Did it happen to anyone else or does anyone know what could it be? What else should I check?
1986 D250 318cui

 

Unplug the temp sensor for the gauge, and ground the wire. If the gauge pegs out, the sensor is bad.

 

i wouldn't even mess with the stock stuff. if you want to know the engine temp just buy an aftermarket gauge and install it. the stock gauge is pretty useless even when they work. they don't tell you the temp. they are really not much better than dummy lights. most times they don't help till it is too late.

 

So I tried this and the gauge works well. I bought a new sensor and it seems to be working. Thanks for advice.