My Coolant Temp gauge has always read to be low since I purchased it a year or more ago. I recently replaced the Coolant Temp Sensor and Coolant Temp Sending Unit. Neither of those fixed the gauge to read. I also replaced the Thermostat and flushed the Radiator. THAT... still did not help bring my gauge to read anything. I am all out of guesses other than a wiring fault/short, I am not doubting that that may be the problem, but everything looks good to me. Also, the oil pressure gauge does not work either but the battery and fuel gauge works. What else should I take a look at that I might be missing.

 

Do you have the proper thermostat installed? Mine did that, and putting a proper temperature thermostat in brough the needle into the proper range.

Remember...these gages are more like dummy lights than they are proper gages.

 

This generation truck uses a single wire sending unit for the temperature gauge. If what you changed has more than one wire, it was not for the gauge & more likely the temp sensor for the ECU.

To test the gauge, unplug the single lead & with the key on ground the conductor. If the gauge swings to H it is working & the sender is most likely bad or there is a large amount of corrosion where it is screwed in. If the gauge does not move, there is either a problem in the wiring or the gauge itself.

Welcome to FTE & good luck.