My 2001 passat engine temp drops after driving for 30 min. turn all my fans off and tht helps any ideas?

In the link below it has two suggestion I see. The radiator fan has two speeds one was not working. They were not sure what was changed. They were told the fan has an idle speed and running speed. Could the fan speed control dropping out take out the temp gauge I do not know? The other idea, your car has a bleed plug to bleed the air out of the engine coolant system, air in the engine will make it overheat.
I did have a car one time and the fan relay would drop out after driving a while but to say it dropped out at a certain time, mine dropped out in slow moving traffic I think due to temperature. After engine cooled it would work for a while, I found the problem because when the fan quit working I wanted to check the fuse but touched the relay and it was very hot.
https://www.cargurus.com/Cars/Discussion-t12549_ds628075
The link below has some good info. It also has a comment that the temp sensor sends signal to PCM and PCM sends signal to control fan and signal to gauge.
https://www.justanswer.com/car/150qo-2001-pt-cruiser-cooling-fan-will-not-on.html
Well maybe this may help
https://www.youtube.com/watch?v=9U9eDsmRbqY
https://www.youtube.com/watch?v=url0zrCeyF4
One thing in the video was you have a low speed relay and high speed rely Just some thoughts or things to look at.

Fan wil be controlled by a temperature sensor, if you have been driving engibe will gethot and start the fan running, as soon as you stop driving the heat does not drop so quickly so fan remains running until the temp sensor detects that the temp has dropped below the threshold. If the fan just runs even after engine itself has cooled down may be a problem with temp sensor. suggest to leave car for about 10 to 20 mins after engine is shutoff and then go back and check if fan still running

Check the cooling fan, thermostat or radiator. I'd start with the basics and check to make sure cooling fans kick on. If they do, remove the thermostat and recheck. If it still fails and bottom and lower radiator hoses are hot then you have a plugged radiator

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_677dced97ad9bddf

check it the heater control is allowing hot water through the heater core.(turning the tap on )

This could also be a faulty fuel pump relay. I had a Honda Prelude that would not restart when hot, but if I let the engine bay cool down for 10 minutes, it would start no problem.

Maybe your radiator is clogged.

you could have an air lock would bleed heater hoses

To start with check the coolant level in radiator...Your vehicle is equipped with a head temp sensor that is designed to shut motor down before it reaches temp. that will result in engine damage..If level is ok then i would look at the water pump at being your next culprit.In either case i would definetly check your temp. sending unit to make sure its operational due to the fact you state that vehicle doesnt get hot...Another thing you can check is to make sure that your cooling fan turns when car gets hot...If fan doesnt come (after you have made sure coolant temp sensor is operational) check fan relay located in power distribution box in engine compartment...

It is OK for them to stop, a lot of cars get the fans going as a default, then once the computer checks everything, the engine temp is still low, the fans will shut off, and come back on when needed. Keep an eye on the temp gauge, and notice that the fans will come on when you stop at a light. Or city driving, they should never come on when cruising. And a lot of times they will run after you shut the car off. Just till the temp drops. Hope this helps.

The sensor is located at the radiator. follow the wire from the fan to the plug on the sensor. I hope this helps.