Seedster

Our '04 530i's AC blows warm at idle when the car is not at operating temp. AC has been charged to operating levels.

The aux fan doesn't turn on immediately when the AC is turned on...only when the car warms up. As soon as the aux fan kicks on, the AC blows icy cold. No codes via my code reader.

It can't be the fan switch on the lower hose b/c that does it's job when the coolant reaches operating temperature.

Is there a relay or possibly another switch somewhere that I should be looking for. Any assistance would be greatly appreciated!


Regards,
Saeed

Notheld

Disco the coolant sensor and check if the Aux fan spins? If it doesnt then it may be your Aux fan.

Could be a number of things at this point. FSU comes to mind

twh

Check this out:
A/C and Aux fan won't turn on ... sometimes

https://5series.net/forums/e60-discu...1/#post1222174

I'm guessing the fan turns on finally since the outlet coolant sensor finally reaches the temp that turns the fan on. The fan should turn on immediately when turning on the A/C as long as the outside ambient temperature is greater than 50 degrees F. The A/C blows cold once the fan turns on since there has to be air movement over the condenser coils for it to work (unless you are at highway speeds).

Seedster

Why would the fan spin if I disconnected the coolant sensor? That doesn't make sense. My assumption is that the coolant sensor in the lower hose is working just fine - in fact, I think it's the only reason the fan turns on in the first place once the car reaches operating temperature.

If it was the FSU, the blower wouldn't work. The blower works perfectly fine at all speeds.

Seedster

Thanks for the links! Marcboogie from the first link has the same exact issue as me. I'll PM him on BF and see if he found a solution. I wasn't aware there was a pressure switch on the low side. Does it directly control the aux fan operation? If so, I'll check it out.

The second link seems to allude to the same thing. I pulled a AUC code (9C54) about a month ago and replaced the AUC sensor, but unfortunately that didn't help (the code did go away though).

Still digging

twh

I saw a screenshot somewhere else where INPA shows you what the A/C sensor is telling the car.

Another thought is if you knew the A/C sensor pinout, you might be able to look at the output and see what it is saying or even simulate a good sensor output.

KyleB

subscribed, have had the same issue since I bought the car in 2012, never bothered to investigate it thoroughly.

AC system like OP was checked and is at the correct amount of R134a, coolant temp sensor is new, aux fan works just fine but only begins working when engine temps call for it.

Notheld

Saeed , just trying to help you. Your making assumptions that may not be entirely correct.

Seedster

Totally understand and I sincerely appreciate all the advice! I'm not writing anything off at this point.