Fans keep running when engine is cold or car turned off

[omer]

I have Statesman WH II (actually left hand drive i.e. Caprice 2002). I don't know what happened but when I turn on my car both fans start to run at full speed even if engine is fully cold and even if I switch off my car then fans run forever which kill the battery. If I move the key in ignition mode in order to start the engine but without starting the car and I remove the key then the fans stop immediately..

What could be the reason ? Has anyone experienced such issue ?

Yesterday the mechanic removed the radiator to replace the crankshaft pulley which was terribly overheating the car which kept sometimes the fans running for few minutes after car being turned off but then used to stop by themselves but now they keep running for infinity ..

 

[Nut Kracker]

Check the connection on the coolant temperature sensor.

Years ago, I disconnected my temp sensor, to see if the after market gauge I installed, would work with the factory sensor and the fans came on straight away.

 

[omer]

I think the problem was air in radiator
during replacement of the crankshaft pulley the lazy mechanic removed the radiator then he re-installed it and added the coolant..
I think the thermostat was closed and air was struck inside the engine which was circulating in it and the temp gauge was acting insane ...
I removed one small pipe which was sending hot water out of engine into reservoir and started the car and disconnected the fans so the thermostat opened due to intense heat and all then air stormed out which was struck