Temp reading low

[Kodjo]

Hi,

The temp reading on my 1969 Avanti, Chevrolet 350, is a bit low. Even after 1 hour of highway it read well below 140F. I can not think of any mechanical reason in the engine so I suspect the sensor or the gauge.

The connection with the sensor is good. I would like to check the sensor. Does someone knows the resistance values?

Any other explanation?

thanks, Kodjo

[pantera928]

Could be that the thermostat is stuck open

[Kodjo]

Could but it is not old, maybe 6 weeks. It worked before but I’ll check. 

Edited November 21, 2021 by Kodjo

[adamderosa]

If you have access to an infrared thermometer you can take a reading at the thermostat housing and compare it to the gauge reading. If they both read low after the engine has been run a while you likely have a thermostat issue. If the infrared thermometer reads operating temp (180-ish) then you have a gauge issue. 

[Kodjo]

Yeah, I can do that. I would like to measure the resistance from the sensor. Does nobody know the values?

[adamderosa]

Sorry I don't know the resistance value range of the temp sensor. But, if you remove the wire from it, the gauge needle should go to one end of the scale, and if you then ground the wire the needle should go to the other end of the scale. This will at least tell you if the problem is in the sender or in the gauge and/or wiring. I went through some notes of mine and many years ago I replaced my sender with a NAPA # 170-1566. This does not seem to be in their system anymore but perhaps someone at NAPA could help if needed.