Temp gauge stuck - diagnosis?
 

Hi,

My temp gauge (73 Trans Am rally gauges) has gotten stuck at around 100 degs.

Doesn't move when I turn the engine off, with cold start, freeway running, or even when I remove the key.

It doesn't move when I disconnect the green wire from the sender.

All other gauges working OK, but I think the dash bulbs are out too. Maybe related...

Is this likely a to be:
a) a faulty sender
b) faulty gauge
c) electrical wiring

Just wanted your expert opinion before I 'deep dive' into dash removal/gauge disassembly. Electrical issues are not my strength!

Thanks

With the switch turned ON: Try grounding out the sending unit wire with a 'cheap' test light. You could touch the sending unit wire straight to ground BUT it may slam the guage, to hot, hard enough to make the needle come loose.
If the guage moves to hot while grounding the sending unit wire......Time for a new sending unit.
If the guage doesn't move to hot with the sending unit wire grounded......Could be anything from the gauge itself, printed circuit messed up, poor connection at the cluster plug-in/connector, etc.,..

If you have to pull the cluster out, need to do some more testing for dash light operation before you pull it out. We can cross that bridge when you get there.

Clay

Thanks Clay

I've borrowed a multimeter (sorry no test lamp)

What resistance values do I look for when cold?

Have someone sit in the car with the key turned on. Since you don't have a test light, just touch the sending unit wire to ground. Just brush it lightly to start with in case it tries to slam the needle hard right. If the needle moves right/hot...the sending unit is probably bad.


Sending unit at different temperatures is about all you'll be able to check with a multimeter.

I do not have the specific ohm readings for the sending unit. But here's a link to a thread that has some info that might get you close. The whole thread has some good info in it. The very last post has sending unit ohm readings for different temperatures.

http://forums.maxperformanceinc.com/...p+needle+stuck

That link is for a 69 GTO so most of the info doesn't apply to 2nd gen birds. Our birds only have two connections for the temp guage where the GTO has 3 or 4. Sending unit values should be close though.

First thing to do is see if the needle will move. Let us know what happens and will go further with more testing. Cluster will have to come out to check the guage, printed circuit and wires going to it.

May have the same problem the GTO had in the link above.

Good luck and hopefully it's just the sending unit.
Clay