Hi I recently bought a 2005 530i I'm suspecting that the radiator fan that cool the system down is not working properly
i had the thermostat sensor and temperature sensor replaced. but the car keep overheating.
I'm driving with the A/C on all the time because that will turn the fan on, if I turn the A/C off and keep driving whenever I turn the engine off
I don't see any signs off that fan working on to cool the engine down. I'm thinking that my overheat issue is related with that fan not activating properly during the driving period.
Anyone knows what that could be??? or how can I really diagnoses the fan.

Thanks

Do you have one or two radiator fans in your car?

If the fan(s) run while the A/C is on then the fan itself is not the problem. Its most likely a temperature switch that is either bad or not connected.

You could rewire the fan so that it stays on all the time - otherwise you are going to have to trace the wires to locate the switch. GL

my car has only 1 fan... I replaced this temperature switch. It's located
in the left down hose right??

I don't know where it's located on a BMW. My guess is the switch would be located somewhere near the engine block. Its a simple mechanical switch that actually touches the block - when the block gets a certain temp it closes the switch circuit and turns on the fan. The switch should have two wires, one of them connecting to the fan. Check to make sure both of these wires are connected properly becasue a loose or bad connection will also cause your problem.

I'm sure there is a diagnostic process chart that a (real) independent or dealer BMW shop would use. But there are sooooo many sensors and switches that talk with computers etc in these cars the DIYer is at a big disadvantage. You may go thru tons of parts trying to luck out and replace the faulty one.

IMHO, if you don't get it figured out with the first go, you may be spending more money replacing good parts than you're trying to save by avoiding a real diagnosis.

BTW, the last time I went thru this exercise with an Audi TurboQuatro it was a resister block that permitted multiple fan speeds. That was hidden away on a frame rail far from the radiator/fan!