I bought the one that is supposed to be calibrated for the correct application but my gauge only reads about 100* when warm. I shot it with a heat gun and it reads about 160* like it should.
Anyone know where to purchase a sending unit that works right?

 

I got mine from LetricLimited...I can't say for sure it is correct as I have only benchtested and have yet to fire up the motor for a real in car test. One thing to be sure of is that you have full voltage at the gauge. A bad connection can messup the reading. Measure the wire where it attaches to the sender (car on but sender wire disconnected from sender) with a voltmeter it should read full battery voltage or more if the alternator is running 13.8 batt to about 14.2 alt. Also check the resistance from the body of the sender to ground should be zero ohms, if both of those readings are correct you have pretty much narrowed it to the sender or the gauge.

One thing to note is that in the original gauges there was an external wire resistor on the back of the guage and many of the replacement gauges specify you NOT to reinstall the resistor. If you have an old gauge the resistor could be bad or if you have a new gauge you might have a present/absent resistor issue. And of course it could all be the sending unit. I plan to calibrate mine as a system once it is installed. In all truth this system is only an indicator and is only close to right at one small range on the gauge, the trick I think is to get that range to start right around the correct operating temp say 180 degrees.

Darren

 

Me too, the one I bought resulted in 140 on the gauge but 160 on the IR gun. I installed a used one I pulled out of my old station wagon when I replace its gauges with autometers.

 

After a rebuild, my brand new engine (in my '65) seemed to be running in the 260 range. After checking with an IR gun, and finding an actual temperature around 200, I became aware of this sending unit problem.

I was referred to "Corvett Clocks by Roger" who supplied me with the correct sending unit and subsequent checks with IR show that the guage is pretty accurate.

 

Try the Wells TU5 at Auto Zone,$5.99, worked for me.

 

I tried the limited and wells (several) and all read differently. Some high and some low. I finally gave up and just know via IR what my temp is in relation to the gauge.