Temp gauge reading low. Replace thermostat?

lsupcar · #1 10-29-2019, 01:31 PM

Just recently noticed that the engine temperature gauge in the dash cluster is reading low. It usually reads just under the 3 o'clock position. Now it is at about the 4:30 position. Moves up or down slightly depending on driving situation. Also, not much heat from the heater.
Should I just presume it is the thermostat and replace it?
Anything else it could be that should be ruled out?
Thanks.
Bill Z

oab_au · #2 10-30-2019, 04:11 PM

Could be the sensor unit, there are two on the rear of the crossover pipe, one for the ECU one for the gauge, the gauge one has a single wire to it.

Trevor · #3 10-30-2019, 10:20 PM

In order to test the gauge, short circuit the sensor connection to ground and check for a full scale or zero reading. Could be either depending on if a bridge or direct circuit is involved, but full scale is most likely. Report back on the the result.

You can test the sensor by removing it and running a connection wire between its body and ground and then holding it in heated water with its insulated connector clear. An electric jug/kettle makes it easy to bring the water slowly to the boil.

You can extend the connections to the car wiring with lengths of insulated wire to make things easy. If you have a suitable thermometer you can record an accurate result, but even without this, you will get a good idea of what is going on.

This can be quite a fun experiment if you have the time and you will then know exactly what is going on. LOL

PS. You report ' Also, not much heat from the heater." Is the gauge in fact correct ? Please consider the overall picture.

johnsvx · #4 10-31-2019, 11:13 AM

I am not sure how to test it, but at least others do. I do know that the heater wont blow hot and the temp gauge will be low if the thermostat is stuck open or opens easily. Its also a fairly easy thing to check and change. Just my two cents.

lsupcar · #5 11-17-2019, 08:08 PM

Follow up.
Replaced the thermostat and gasket this weekend.
The old one was stuck open.
With the new one in, the coolant temp gauge is back to normal.
Thanks.

oab_au · #6 11-17-2019, 08:20 PM

Quote:

Originally Posted by lsupcar

Follow up.
Replaced the thermostat and gasket this weekend.
The old one was stuck open.
With the new one in, the coolant temp gauge is back to normal.
Thanks.

Thanks for coming back with the answer.

Blacky · #7 11-18-2019, 02:45 AM

Good news. Simple and affordable.