radiator fan always on

[bigtisas]

I noticed the radiator fan turns on as soon as I start the car. It happens everytime. Even when the engine is still cold in the morning. Outside air temp was around 64F (17C) and the temp gauge is at blue mark.

Shouldn't the fan only turns on when the engine gets hot?
Faulty themostat?

[Jon K]

Do you mean the aux fan?

The mechanical drive fan will always be "on" obviously - not to say you didn't know that.

The aux fan turns on with AC and hot temps. Could be your sensor or resistor bad.

[DaveVoorhis]

I'd suspect a defective sensor on the right-hand side of the radiator or a stuck relay. Check the sensor by unplugging it. The fan should stop. If it doesn't, try unplugging the relays one at a time in the auxiliary relay box in front of the fuse box. If that stops it, you've got a bad relay.

[bigtisas]

Thanks. I'll check the sensor and the relay.

[Amskeptic]

I noticed the radiator fan turns on as soon as I start the car. It happens everytime. Even when the engine is still cold in the morning. Outside air temp was around 64F (17C) and the temp gauge is at blue mark.

Shouldn't the fan only turns on when the engine gets hot?
Faulty themostat?

Try pulling the relay and do a continuity check through the usual 30/87 contacts. There should be none. They often stick due to overamperage.
Colin

[bigtisas]

Now i understand why my car takes so long to warm up the engine. It's because the fan (I believe the aux fan) is always on. It typically takes 10 mins to just pass the blue mark on the temp gauge.

[winfred]

the aux fan will run on low whenever the ac switch is on regardless if the engine is running or if the ac works, you can test for the sensor by just unplugging it plug's brittle don't manhandle it) theres two relays a high and low speed in the smaller box on the left fender well forward of the fusebox, i can't remember the positions but theres only 2-3 relays in that box, try smacking them first then you can unplug them one at a time till you find the offending relay that shuts the fan down, then switch it with another relay that has the same pins from the car and see if the fan still runs

[Blitzkrieg Bob]

failing, it should warm up pretty much the same regardless of the fans.

[Adnan]

I noticed the radiator fan turns on as soon as I start the car. It happens everytime. Even when the engine is still cold in the morning. Outside air temp was around 64F (17C) and the temp gauge is at blue mark.

Shouldn't the fan only turns on when the engine gets hot?
Faulty themostat?

Hi,

I checked the schematics and concluded that it was a faulty high/low pressure switch on the A/C system (located just under the windshield washer fluid reservoir). In other words, disconnecting the switch solved the problem. I bought a new one from BMA, pulled the R12, popped the new one in, recharged the system and all's well.

Good luck!

Regards,
Adnan

[bigtisas]

I checked Bentley. I was referring to the mechanic fan (the fan between radiator and engine), not the aux fan. Sorry for the confusion.

But how come the mechanic fan always on? In my old car (an Acura Integra), the fan only comes on when the engine is hot. And it stays on after ignition is off if the engine is still hot. The e34 mechanic fan seems like "attached" to the ignition regardless of the engine temp. ???