water temperature gauge gone wacky
Posted: Thu Nov 04, 2010 9:52 pm
I need help troubleshooting the water temperature gauge in my '98 Legacy wagon. Here's what's happening:
The needle does a few different things, such as going past "H" and staying there, or going to "H" and bouncing around, bouncing around the 3/4 hot area, or sometimes reading normally. I replaced the coolant temperature sensor (the temp gauge is connected to this sensor) with one that worked from my ss (parts catalog shows they are interchangeable) and there was no change to the needle's readings.
I searched and searched everywhere I could think of and finally found a thread with a post that suggested disconnecting the sensor's wire and if the needle stayed at "C" it would mean one thing and if it went and stayed past "H" it would mean another thing (although I forgot which reading would indicate a faulty sensor and which would indicate wiring troubles; and I'm not yet able to find that thread again). So, I disconnected the wire this morning and drove a few miles. The needle never moved past "C". "Great!" I thought. I went into the store, got back in the car, started it, and the needle immediately swings past "H" and bounces around the "H" and stayed there while I did other errands and on the drive back home (about 10 miles of driving).
If the sensor is disconnected, how is it that the gauge is apparently getting varying voltage to it? Is it faulty wiring or a faulty gauge? Or something else or a combination? How do I troubleshoot these errant needle readings?
Any help is much appreciated! Thank you!
The needle does a few different things, such as going past "H" and staying there, or going to "H" and bouncing around, bouncing around the 3/4 hot area, or sometimes reading normally. I replaced the coolant temperature sensor (the temp gauge is connected to this sensor) with one that worked from my ss (parts catalog shows they are interchangeable) and there was no change to the needle's readings.
I searched and searched everywhere I could think of and finally found a thread with a post that suggested disconnecting the sensor's wire and if the needle stayed at "C" it would mean one thing and if it went and stayed past "H" it would mean another thing (although I forgot which reading would indicate a faulty sensor and which would indicate wiring troubles; and I'm not yet able to find that thread again). So, I disconnected the wire this morning and drove a few miles. The needle never moved past "C". "Great!" I thought. I went into the store, got back in the car, started it, and the needle immediately swings past "H" and bounces around the "H" and stayed there while I did other errands and on the drive back home (about 10 miles of driving).
If the sensor is disconnected, how is it that the gauge is apparently getting varying voltage to it? Is it faulty wiring or a faulty gauge? Or something else or a combination? How do I troubleshoot these errant needle readings?
Any help is much appreciated! Thank you!