Test for failed coolant level sensor?

crash813 · Post by **crash813** » 25 Jan 2012, 16:48

Anybody know a test to see if the coolant level sensor is bad? Low coolant light is on but the expansion tank is full. Just replaced the tank, guessing leaking coolant or the removal/reinstall might of broken sensor but would like to test it if I could before ordering a new one.

thanks

Post by **jblackburn** » 25 Jan 2012, 19:02

That's your test. The sensor's bad if the coolant is full and it's still showing the light.

Shemp · Post by **Shemp** » 25 Jan 2012, 19:21

I had the same thing happen when I replaced my tank. Replaced it with a new sensor, and the light went off. The only downside is the replacement was an aftermarket brand and it doesn't trigger the light until the coolant is at a much lower level than the original sensor worked at. I'm planning on putting a Volvo sensor back in soon, as I don't really trust the one that's in there now.

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Post by **mikealder** » 26 Jan 2012, 10:56

Slide the expansion bottle off its bracket leaving the pipe connected and the cap on, turn the bottle upside down and give it a good shake, refit bottle to the car and check the low coolant light is off, if it is the sensor was stuck, if its still on the sensor is shot - Mike

db130 · Post by **db130** » 26 Jan 2012, 12:43

pull the sensor from the bottom of the coolant tank - is the light still on? then it's a bad sensor

just because the light is on when the coolant is full doesn't make it a bad sensor - if the float inside the tank is stuck at the bottom, it will still trigger a light. however, since crash813 already replaced the coolant tank(presumably with a new one?) you are most likely looking at a faulty sensor.

darkember · Post by **darkember** » 09 Jun 2013, 01:31

db130 wrote:pull the sensor from the bottom of the coolant tank - is the light still on? then it's a bad sensor

just because the light is on when the coolant is full doesn't make it a bad sensor - if the float inside the tank is stuck at the bottom, it will still trigger a light. however, since crash813 already replaced the coolant tank(presumably with a new one?) you are most likely looking at a faulty sensor.

Dependant on the model these sensors work on ohms readings & not a float device. A simple multimeter will be able to verify if the sensor is faulty or not.

Post by **abdomar528** » 12 Mar 2016, 21:13

This thread is so old but I thought I'd comment anyway. Check out my video here:

I bought this new tank online and it was a Volvo genuine coolant tank. After 10 days it went bad. I did this test where I compared it to a new tank and I realized the tanks float mechanism is bad.

Watch the vid and comment!