Does anyone know a test for the coolant temp. sensor?

 

Thanks

check codes

 

wiggle the connector around. if you said your sensor was bad i probably wouldn't believe you...in my 11 years of driving subarus it's always the temperature sensor CONTACTS, not the sensor. replacing the sensor will often cure the problem, but it's usually temporary because the wiring harness that plugs into it will be corroded.

 

here's a mini-write-up i did at www.xt6.net about fixing the water temp sensor:

 

i pulled the water temperature sensor out and soldered wires directly to the terminals of the water temperature sensor (see picture). Then i put heat shrink tubing around each terminal and installed the sensor with male/female (engine side) electrical connectors so i can remove or replace th sensor. when i cut the wire on the engine side the copper wire had the typical green corrossion. i cut it back a few inches and noticed it was still green. The insulation was intact, it had the factory electrical tape all wrapped around it, but it was corroded back a few inches. i pulled the wire (along with the oil pressure sending unit wire) out the back of the motor to have a look. i cut off more and noticed it was also green. so i cut off all the way to the engine electrical harness and installed new wiring from there. car now starts, runs and idles much better than before. i guess when the harness gets old and corroded, moisture gets up into the wiring (under the insulation) from the wiring harness and begins to corrode the wire. funny thing too....the wire was very very hard where it went through the engine. i would snap as soon as i went to cut it, very brittle. but when it got to the engine harness (towards the back of the engine) it was more pliable and like normal wire. i guess heat (and moisture possibly) made it brittle over time. in any event, something to look at if you have electrical or sensor problems or keep in mind. glad to never think about that water temperature sensor again, that thing was annoying! i think every XT6 i've ever owned has had that problem.

From the 89 Factory Service Manual:

 

"Put the thermosensor in water of various temperatures and measure the resistance between terminals using a circuit tester.

 

Water Temp: .................Resistance:

14 degrees F ..................7-11.4 K ohms

68 ................................2-3 K ohms

122 ...............................700-1000 ohms"