Temperature gauge not working properly

[SK]

The temperature gauge of my 63 Eldorado does not work properly.

It goes slowly all the way up and stays there, while the true temperature is around 155-160 F (water in the radiator and/or the top of the thermostat housing).

Where should I start to solve the problem? The gauge itself, the temperature sensor, or the wiring? Or something else? The sensor is a new (aftermarket part) and the thermostat worked fine when I tested it in a saucepan. 

Many thanks

-Samu

[Jason Edge]

I received my 5 sending units today and they are spot on in terms of expected resistance reading and operation in my 64 Coupe de Ville. The 4 extras will be for sale for $20 each ($15 for Chapter Members).  I also of course still have a good used one that came out of my car. Here are some pictures:

[Jason Edge]

That is good news, Bob. I ordered 5 and will do a comparison with the original I have in my car.

Jason. 

[Robert Schles]

It recently bought an ACDelco temp sensor from Rockauto https://www.rockauto.com/en/moreinfo.php?pk=343530&cc=1320309&a...

It is working like it should, reading the temperature correctly.  

[Jason Edge]

That is good news indeed. Now, if they would only start reproducing the correct replacements. The list if defective replacement parts is growing!

[SK]

Better late than never:

I finally plugged in the good used temp sensor bought from Jason, and the problem is solved.

The temp gauge stayed now at the lower 1/4 mark. The weather was allready quite cold (~35 degrees Fahrenheit), but with the previous sensor the gauge went up whatever the outside temperature was. 

That test drive was the last one for this season. Case closed and a good start for the garage season.

-Samu

[Jason Edge]

As Chris noted, most new temp sending units (at least the ones from China) are mis-calibrated and give a false hi reading. I have a good used sending unit that gives a resistance in the correct range I have seen for good sending units over the years for $20. I only have the one for now and the demand has been growing. I can ship to US destinations for $10 for a total of $30.  If you want it, shoot me an email to [e-mail].  

[Chris Codd]

I was just talking about this with Jason the other day as my car is doing the same thing. The new temperature sensors can be junk straight out the box. I believe Jason might have an extra used original one. I just ordered one from him yesterday.