When I cleaned up my engine and hosed everything off, my coolant light came on and stayed on for two days. I think that some water got in the sensor. After things dried out, it turned off on its own. Might not apply in your case, but just my experience.
I am having the same problem with my 2000GT radiator light. For example: this mornig on the way to work, no light; on the way home around 4:30 in the afternoon, the light came on after a while of driving.
The car is not running any hotter than before. I did spray the motor off a couple of weeks ago. I guess I will unplug the sensor and plug it back in to make sure it has a good connection.
When I took off the tank I looked at the sensor with the bouyant styrofoam looking object which sends a signal to the computer and tells it how much radiator coolant is there. The sensor did not have any styrofoam looking material on it and when the radiator was full of coolant, the moving object was at the bottom of the tank. That was causing my problem. I replaced the tank and it was fine. That shows you to replace your coolant because I did not for years and it ate away at the styrofam and caused me to replae the reserivour tank.
I would unplug my comp. and when I startted my car the light was not on. Then after I reached a certain temp. the light would come off. Maybe you have a little left and when it heats up it is not able to stay afloat so then it sinks and the light comes on. Hope that helps like it helped me. The reserviour tank is not to expensive but it is not cheap either. It cost me around 60.
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