Temperature gauge issues?

[drowens1]

When I drive my 6.2 HMMWV the engine temp is fine for a long time. Then as I keep going the temp begins to climb until eventually the temp gauge is full travel. I have a laser temp meter that I take temperature all over the engine and radiator and the highest temp registered is 205* at the t-stat housing. So I don't feel as though I'm actually get a high temp. But what might the problem be? The gauge or the sending unit?

 

[Daves86]

When I drive my 6.2 HMMWV the engine temp is fine for a long time. Then as I keep going the temp begins to climb until eventually the temp gauge is full travel. I have a laser temp meter that I take temperature all over the engine and radiator and the highest temp registered is 205* at the t-stat housing. So I don't feel as though I'm actually get a high temp. But what might the problem be? The gauge or the sending unit?

My 86 gauge would be fine then start bouncing 200 to 240. I changed both the meter and the sending unit to no avail. For mine I had to install the grounding kit. I started with the sending unit cause it was the less expensive part.

 

[Retiredwarhorses]

I’ve had same issues many years go...the wire from the sender had a high resistance short, I ran a separate wire and it fixed the issue.
you can do same to test it....just run if from the sender to gauge, see if the issue goes away.

 

[papakb]

The electrical system feeds 24v to the temp gauge and from there it goes directly to the sending unit and ground. The system is measuring the current flow thru the sensor as it's resistance changes with the temperature of the block. When the system has all good conductivity everything works well but if you have connectors that are starting to corrode or oxidize or if you have wires that are starting to fail that resistance gets incorporated into the calculation and causes the gauge to show incorrect readings. The sensor in the temp gauge is the one in the block behind the alternator, not the one on the crossover pipe. There is no ground to the temp gauge because it's measuring current flow so the only ground in the system is the ground to the block and if that's bad usually you have other indications but it never hurts to make sure everything is clean and tight.