The gauge stays in the middle when the car is on.

Even when only the ignition is on, it goes to the middle. Then back down when the car is off.

Goes straight to the middle on a cold start, and stays there when warm and never moves (until I turn off the engine).

I unplugged the coolant temp sensor (CTS) and turned on the ignition (not the engine) and the gauge went to the middle again. This also kicked on the cooling fans.

Then I unplugged the temp sender unit (right next to the CTS) and the gauge still went to the middle again when I turned on the ignition.

What is wrong here? Any ideas?

Edited September 16, 20205 yr by Johnny Subaru

That is odd for it to go to the middle on a cold engine.

The Temp Gauge is supplied 12v and a Ground and another ground from the wire to the single wire Temp Sensor. Unplugging the Temp Sensor wire should make it stay at cold with the key on.

Sounds like the Gauge itself is bad. I think I would change the Temp Sensor too, just in case it caused the Gauge to go bad.

If the sensor wire is grounded somewhere the Gauge would go to hot, not the middle. To go to the middle it would have to be a certain amount of resistance to ground and that is very unlikely.

I had to change the fuel gauge on our 95 because it was stuck on full. So they can go bad. Most of them never fail. Actually, the Temp and the Fuel Gauges work on the same kind of circuit. A hot and a ground and a variable resistance to ground.

maybe use a 1.5 or even a 9v volt battery to see if you can force the gauge to change at all???

 

weird

What car is it. COuld be curious to put a OBD reader on it and see what the ECU sees as temp. Then you can decide if it is Temp sender, wire, grounding or indicator. 

 

Thanks to everyone responding to this post. We figured it out!

I replaced the single wire sending unit, that was not the problem. 

The gauge itself was the issue. I pulled the cluster, and then pulled the temp gauge off. Swapped it with my other '99 Legacy and did tests with those gauges. The gauge from the '95 was bad. Went to the wreckers and snagged a gauge off a 95 Legacy, cost me $10 and about 4 hours trouble shooting. 

Happy endings.

Thanks for reporting back.

Glad to hear it is fixed and thanks for letting us know.

I think it is a good thing you changed the sending unit.

When I changed our fuel gauge I ordered a new one because it was really cheap. I couldn't believe it, 18 bucks new from Subaru.