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Topic: Reading car coolant temp sensor (Read 101 times) previous topic - next topic


Jun 25, 2020, 01:00 am Last Edit: Jun 25, 2020, 01:01 am by oferr


I am trying to read the car coolant sensor resistance (voltage) but I want to try and do it without affecting the car dashboard that is using the same sensor. The sensor has one terminal and is getting constant 10.3 V from the car dashboard instruments cluster. At room temperature (20c) the resistance is 1020Ω when the engine is hot the resistance drop to around 30Ω. Below is the circuit I thought about. I think that I do need another voltage divider in the case of low temp and assuming I will get the 10.3V. In that case, my divider will output 3.3V

Attached please see the circuit I am thinking to use. Will that work?




Two additional measurements I just did.
1. when measuring the voltage on the sensor the voltage goes down as the resistance is going down. So at 44 Ω the voltage is going down from 10.2V to 6.5V
2. measuring the voltage on the sensor with a Fluke is not affecting what the car dashboard is showing. So there is a way to do it and minimizing the effect on the dashboard function.

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