tfr1

Have been experiencing intermittent problems with temperature gauge.

Probably not gauge, likely the sensor, but I am not sure.

Seems related to A/C operation.

When operating truck with A/C on, gauge will go to full HOT position from "straight up" normal in a matter of seconds. A warning alarm sounds and dash says "check instruments".

If I pull over and turn off truck and immediately back on, gauge returns to "straight up" normal position.

I usually get an indication of an impending problem because gauge issues are often preceeded by the lack of cold air coming from the the A/C vent.

If I notice temp gauge rising in time, I can turn off A/C and turn blower to high speed and set temp at MAX heat. This usually returns temp to normal position.

None of this produced an engine check warning or code.

Truck has served me flawlessly for nearly 300K miles.


What would you check next?


TFR1

tfr1

So maybe I should change the sensor to see what happens?

Anybody know where temp sensor is mounted?

Why does it seem related to A/C operation?



TFR1

iowagooser44

Old school before computers....what about your thermostat??

barjrob1972

No input other than the typical sensor, thermostat, clogged radiator comments. Pretty straight forward.

300k flawless miles? That's impressive.

bigmike66

with 300k on it, its possible some wiring has rubbed itself raw and is shorting out. sounds like temp sensor is getting voltage from the a/c. try following the wires from the a/c compressor and see if they are possibly shorting out with the temp sensor signal wire. don't know if this is possible as I don't know where the temp sensor is located, but makes sense to me. if that's the problem it explains why when it happens your a/c shuts off and temp guage spikes.

alsatropine

iTrader: (2)

Check your Clutch Fan. Pop your hood and crank the truck. Let it run for a sec and then shut it off. Watch your fan to see if it stops within a few seconds or if it free spins. If it free spins then you need a new fan clutch. That happened to me on a Explorer. If I ran the A/C the motor would try to overheat instantly.

tfr1

Sorry for the delay in responding.
I changed the coolant temp sensor for good measure, but as alsatropine suggested, fan clutch appears to be the deamon.

Seems obvious now, but never considered it.

Truck has been so good to me, I never expect failures.

Thanks for the help.

TFR1

tfr1

300K flawless miles might be a slight stretch of the truth but not by much.

One fuel injector, fuel pump relay module, 4 sets of spark plugs, tires every 75K miles, oil and filter every 5K miles, one pair of front rotors (don't remember how many pad changes), drivers side window regulator. Also replaced front 4WD hubs at 235K miles. Not a failure, just getting noisy.

I have performed all the above service except tire changes.

Can't wait to get a new one when this one starts letting me down.

alsatropine

iTrader: (2)

Not a problem. You can do it yourself and save money on labor. You can get the clutch fan tool on loan at autozone. Just remember the nut that attaches the fan to the water pump is reverse threaded. Might take an hour if you know how to work a wrench.

Bmuch1883

I replaced the cylinder head temp sensor and did a guage sweep and temp guage began to work but after I crank my truck the check guage message comes on about 30 seconds later and guage drops below C. Any help