mechanical v/s electrical temperature gauge

callbald

callbald

Senior Member
I am looking at a mechanical temp gauge and looking for installation advice. I see some install it in the intake manifold verse in place of the normal block location. I have been having nothing but trouble trying to get the original gauge to work correctly even after replacing the sensor and constant voltage regulator.
 
Most of them are installed in the intake manifold just before the thermostat. Since that would be the temp the Tstat would see.
 
Have you cleaned the terminal junctions, think you should have two black rubber plugs on firewall around Left hood hinge. Almost all your underhood wiring passes through those plugs. Gang bullet connectors, they can corrode.
 
The accuracy of electric gauges is relative. What I mean is any number of out side factors will effect the reading. Go to Lowes or Home Depot and get an infrared temp reader gun. They are in the $20 range and can be a huge trouble shooting tool. Get your car up to "normal" operating temperature and shoot the top of the t-stat housing or the hose itself and see what the actual temperature is. Now you will know the effective reading on the temp gauge with respect to the actual temp of the engine.
 
I have a Harbor Freight infrared temp reader gun and get readings of 185 on the radiator and 165 off the hoses. Fully warmed up the OEM temp gauge reads just above the cold bar. I reinstalled the temp sensor just in case and same results.
 
Can't explain why, but a 66 Falcon Ranchero I built was a 289 originally. Put a 302 EFI into it. The temp gauge read just short of the hot bar from the get go, t-stat said it was 195 all day long. I used the sender from the 289, fuel gauge worked perfect, grounds were all good. Only thing I could come up with was the gauge was set to run middle range at 185 and the 195 in the 302 made it show higher. The other thing I reasoned was the intake on the 289 was cast iron and the 302 was aluminum?
 
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