Coolant Temperature Gauge

[AKRIVIERA79]

My coolant temperature gauge is not working in my 87 Syncro.
The warning light does not flash when I start up and the needle does not move at all.

Any suggestions on where to start the trouble shooting process? Where does the coolant temperature gauge reading from/attached/wired to?

Thanks for your help from AK.

DG


1969 SQBAK
1987 Syncro

[r39o]

It is attached to the flex circuit board on the back of the instrument cluster. "Maybe" one of the contact nuts fell off. In any case, I think you have to look in the back of the instruments. The description for trouble shooting is in the Bentley. There is also a test for the flashy LED in the best threads stickies.
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[tencentlife]

First off, does your fuel gauge behave normally? If it is reading either empty or full all the time, you probably have a bad voltage stabilizer. If the fuel gauge is reading normally then you can test the temp gauge system.

Start at the sender. It is installed in the thermostat manifold, which is attached to the forward end of the left cylinder head. Lotsa hoses go to it. Low on the left side is the (usually blue) Temp2 sender, for the fuel injection. That is NOT the one you're interested in. The other sender, for the gauge, is installed in the forward end of the manifold. You may need to crawl under the car to get a good look at it. Its connector is usually covered by a rubber boot.

If you get the connector off, there's a couple things you can test. First, jumper the yellow/red wire to chassis ground. Turn on the ignition, the temp gauge needle should go sky high and the gauge LED should flash. If it doesn't, there is a problem in the gauge or wiring.

Whether the gauge responds or not, while you have it unplugged you should check the sender and the brown ground wire with an ohmmeter. The brown ground wire in the plug should have zero ohms to ground. Resistance between the two pins of the sender should be over 500ohms cold, but not infinity. If there is no continuity between the sender pins, you need a new sender.

Check all those things and tell us how it went. If your gauge didn't respond when you grounded the sender wire, get back and we'll tell you what to check next.

[AKRIVIERA79]

tencentlife,

Thanks for the info, but I just got back from a wonderful temp duty in Korea. My coolant gauge is working fine for now, but I have been only back for 3 days.

Thanks again,

DG