When engine is cool the light goes on.... as the auxsix fans kick in it turns off..

I can't find any leaks but it is loosing some coolant.
I checked both tran oil and oil no coolant mixing.

I'm baffled help.

Plus the heat blows cold at idle and heats up as I drive.
Getting tired of this car

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1994 e320 (Charcoal and grey) 140, 000 miles