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Pull the wire off the sender and touch it to ground with the switch on and watch the gauge for movement. It'll tell you which way to start looking.
That will SAVE A LOT of time, energy and frustration!!
Also, you may want to check the t-stat. Had a the very same situation you have (gauge stopped working). After replacing the sending unit, gauge, wire and my sanity....found out the $8 t-stat failed in the open position!!! So if your gauge doesn't react when you ground it, check the t-stat.
No offense, but a T-stat stuck in the "open" position won't cause a temp gauge to "quit working"....it will just take more time to get it to normal operating temperature. [T-stat doesn't SET the temperature, it merely helps regulate it to heat up to temp quicker.] Sending wire pulled off the sender should cause gauge needle to swing one direction; touching that wire to ground should cause it to swing the other direction. If the needle moves with that test, the sender is bad; if it doesn't move, the problem is either: no power getting to the temp system; feed wiring has a problem; gauge is bad.
7T1,
With your test, if you try your test on a cold engine with a gauge and sending unit that work ,what, if anything, does the gauge do? Is there a way to test just the sending unit? I'm trying to come up with a procedure to test each gauge with the engine off. Since it would be good to know that the gauges work before you put the dash back together, and sometimes the engine isn't running at that point.
I'd appreciate you help and information.
Regards,
Alan
The sending unit can be 'evaluated' if you leave it in the block. Essentially, it is a variable resistor...so you can use an ohmmeter to measure its resistance with the car "cold", then warm the car up and measure it again. Memory tells me that the resistance goes down with increased temp [but I could have it backwards]. Anyway, the senders usually fail in "open" mode, where the resistance is very high; I've never had one that 'shorted'...it would probably blow a fuse if that happened.
Hope that helps. P.S. If you just turn the ignition on [don't start it] and try the "open" and "shorted" tests after removing the sender wire, you can usually tell if it is the sender. Any reading on the gauge during that test indicates that the rest of the system is OK.
No offense, but a T-stat stuck in the "open" position won't cause a temp gauge to "quit working"....it will just take more time to get it to normal operating temperature. [T-stat doesn't SET the temperature, it merely helps regulate it to heat up to temp quicker.]
None taken...but at the same time, my t-stat failed in the open position and the temp gauge needle didn't move...even after driving for a couple of hours. I know the t-stat doesn't set the temp but merely regulates it. All I know is what happened to me. It may be because I have a 2-row aluminum radiator that my temp never rose high enough to record. All I'm saying is that if you ground the wire and the gauge reacts correctly, then the problem is either the sending unit or the t-stat. And, once you replace the sending unit, you still have the same problem, then it's got to be the t-stat.
I believe you....but that's very unusual. Must be a hi-capacity radiator with good fan system and hi-flow pump. Even then, I would have thought you would see 130 degrees or more. Interesting.