Jetdriver69

On my 82 5 speed, I can't find the resistance values to check the water temp sensor, not the the temp II sensor in the WSM.

If the sensor checks out bad, would it cause erroneously high gauge temps?

My temp gauge is right in the middle with my new electric fan set up, but an IR temp reading at the water bridge seems low at less than 150F with the gauge in the middle range.

Any help? Thanks

Hold On

Remember, depending on where on the water bridge you aim your IR gun the temp number will change. Think of the water bridge as a mixing chamber for engine and radiator/ bypass water. In the winter, the difference will be much more dramatic. Completely different from normal cooling systems. My stock temp guage reads normal but the digital guage with sensor in top radiator hose reads as much as 50 degrees cooler at that location. Hope that makes sense.

jpitman2

All the temp sensors I have seen on Bosch gear (used for signalling the ecu anyway) run around 3k Ohm cold, dropping to ~300Ohm hot - NTC type - Negative temp coefficient of resistance. Not sure if the actual temp gauge is driven by the same method, but highly likely - as resistance goes DOWN as Temp goes UP, gauge reads higher.
jp 83 Euro S AT 55k

Wisconsin Joe

Temp gauge reads zero with an open circuit (infinite resistance) and pegs hot when the wire is shorted to ground (zero or near zero resistance).

neilh

Correct, resistance drops as temp rises, around 3k cold to 300 hot.