How to test the cold start sensor
06 June 2010, 03:12 PM
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Cold start sensor? If you're referring to an early/mid classic it isn't a "cold start sensor" as such, these cars have two coolant temp sensors, one that feeds the needle in the gauge pack and another connected to the ECU.
On later cars either one sensor does both or the two separate sensors are contained in the same physical package, not sure which way that works.
As for testing, it's just an NTC thermistor, so if you take it off, use a multimeter in resistance mode, and try the sensor both in a container full of icewater, and then warm/hot water of varying temperatures and see what resistance you get. If you have a regular thermometer there to cross-check against, so much the better.
I don't know the exact calibration curve for the Subaru sensors, but as a rough guide you should see around 5.5Kohm at zero degrees celsius, 2.5K at 20 degrees, 1.2K at 40 degrees, and around 0.65K at 60 degrees.
On later cars either one sensor does both or the two separate sensors are contained in the same physical package, not sure which way that works.
As for testing, it's just an NTC thermistor, so if you take it off, use a multimeter in resistance mode, and try the sensor both in a container full of icewater, and then warm/hot water of varying temperatures and see what resistance you get. If you have a regular thermometer there to cross-check against, so much the better.
I don't know the exact calibration curve for the Subaru sensors, but as a rough guide you should see around 5.5Kohm at zero degrees celsius, 2.5K at 20 degrees, 1.2K at 40 degrees, and around 0.65K at 60 degrees.
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