Aircon fan

[Grrrmachine]

Got aircon installed, all charged up and blowing cold, but the mechanic told me the aircon fan should blow as soon as the aircon is turned on. I thought it was only supposed to come on when told to be the radiator switch.

So who's right?

[jmc330i]

With the switch I'm sure. Otherwise what's the point in BMW fitting the switch

[Grrrmachine]

well, the rad is a hi-lo switch, but I don't know if that means off/on slow at 91 degrees/on high at 99 degrees, or something else.

[DanThe]

He is right, with air conditioning on the fan should be running on low speed.

Unless its some aftermarket A/C?

The other possibility is the resistor is burnt out which is common, if you search demlots posts he did once post a part number for the replacement siemens resistor which is used on later cars, and is about half the price of the bosch original

[jmc330i]

Mine came on at low speed at 91 and switched to high speed at 99.

[Grrrmachine]

Simplest thing for me to do is push 12V straight through the fan at its plug to see if it works. If it spins, I'll have to do some more fault-finding in the loom. If not, then I'll check out this resistor.

It's original BMW though.

[Grrrmachine]

Jumped the K1 and K6 relays; hi fan worked, lo fan didn't. One replacement fuse later...