It is any way to check the temperature gage on a 66 ?? according with my radiator temperature gage the temperature stay at 180 and after idling for 15 minutes+ goes to 190, however the gage on the dash goes to 3/4 to H and come back to 3/4 again over and over which make realy very nerveous while I am driving..I am sure that the gage it is defective after 40 yrs however I will like to be able to check the gage before buy a new one it is any way to do it and is the gage to be removed form the instrument panel?? ( the termostat is 180) thank you

 

it may be the temperature transducer. I am not sure what the electrical impedance is supposed to be on these old cars.

 

The most accurate way I have found is to by an infrared thermometer ($25-$40 at NAPA). Let your engine get up to running temperature and take several readings. Shoot at the radiator, the thermostat housing and the cylinder heads. This will give you the most accurate reading of what temp your engine is really running at, then check your dash guage.

My engine runs at 180 but my guage was right before "H". Don't trust the guage. Once you know your true temp you can re-calibrate these older guages but it is a pain and you have to remove them from the dash. Or just live with it and know that your guage is lying to you.

Hope this helps

 

In the FAQ try this link http://www.mustangandfords.com/techarticles/75259/
A good place to start....