Aux fan runs all the time...?

[Adnan]

Hi,

Started up the car this morning ('91 535) and the idle felt kind of rough. A little searching through the old memory banks reminded me that it felt like the aux fan was running.

Sure enough, the fan runs all the time, except of course when I turn off the ignition. As I understand it, the fan comes on when the A/C is on or when the temp sensor in the side of the radiator triggers it.

Could I have a failed temp sensor? Is there another likely culprit I should check for?

Many thanks,
Adnan

[632 Regal]

temp sensor is possible, try tapping the fan relay in the fuse box when the car is idling and see if it kicks off. If so you found the bad relay.

[Adnan]

Hi,

Sorry, it's been a while since I messed around with the car's electricals - is this the fuse box where the LKM is or the rats nest under the rear seat?

Good thought, although it means that the fan and relay were active when I parked the car last night, which they weren't. Unless, of course, the relay is a normally closed type.

Thanks,
Adnan

[Bill R.]

the high speed, they are in their own little relay box up front under the hood
on the left side right next to the orange connector for the airbag impact sensor on the fenderwell.... K21 is the low speed and K22 is the high speed, they are normally open

Hi,

Sorry, it's been a while since I messed around with the car's electricals - is this the fuse box where the LKM is or the rats nest under the rear seat?

Good thought, although it means that the fan and relay were active when I parked the car last night, which they weren't. Unless, of course, the relay is a normally closed type.

Thanks,
Adnan

[Adnan]

the high speed, they are in their own little relay box up front under the hood
on the left side right next to the orange connector for the airbag impact sensor on the fenderwell.... K21 is the low speed and K22 is the high speed, they are normally open

[Adnan]

Hi,

I checked the radiator switch, both contacts were open, as they should be. That then points to the relays.

Could it also be the A/C relay? After all, if the fan is supposed to come on as soon as the A/C is turned on, that relay could be a potential problem. Or is it that a bad relay there would also turn the A/C on all the time?

Thanks,
Adnan

[632 Regal]

tap tap tap....

[winfred]

it's generally a stuck relay and a good wack usually unsticks it, you can unplug the relays that bill mentioned and kill the fan

Hi,

I checked the radiator switch, both contacts were open, as they should be. That then points to the relays.

Could it also be the A/C relay? After all, if the fan is supposed to come on as soon as the A/C is turned on, that relay could be a potential problem. Or is it that a bad relay there would also turn the A/C on all the time?

Thanks,
Adnan