Quote:
Originally Posted by Tommy
And have you checked the accuracy of the temp gauge with an infrared temperature reader? On some cars the gauge will read high if the ground connection between the temp sensor and the engine block is not good (e.g., too much or wrong thread sealant on sensor).
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Most cars I know, if the temp sender has a poor ground (which is not common with a tapered thread) it causes the gauge to read lower than correct, not higher.
The sender is a NTC variable resistor, that becomes less resistance as the temperature rises. The gauge bimetallic strip is in series with the sender, the resistance change allows more current flow, then the gauge reads higher.
A common trick amongst "backyard mechanics" is to add a resistor in series with the sender to make the gauge read lower.
I found a car with a resistor added one day.
Took a lot of convincing to the owner they had a problem.