E60 528i LCI A/C Blows Hot Sometimes

[Jango Fett]

I need guidance on an intermittent AC issue.

The AC works GREAT below ~85F. As soon as the outside temperature gets above 85, the AC won't cool down until I rev it hard or hit the highway. Sometimes it won't cool down even on the highway but this only happens when it's 95+ outside. Even if the AC starts working ok, it blows hot air when I reach a stop sign or stop light.

I've researched countless threads before posting here. Here's my investigation so far:

- This model doesn't have a coolant temperature switch (nothing on the lower radiator hose like many other models). If I could unplug this and force the fan high, I would have already added a switch to to do this.
- The Freon has been checked out and the system is charged properly.
- Compressor clutch engages properly. I monitored this with iCarly OBD adapter while turning the AC on and off.
- Electric fan PWM only operates between 10% and 30% duty cycle. This seems the most suspect to me.. I haven't been able to determine all variables used to calculate the PWM output from the DME.
I believe this is the culprit for blowing hot air when stopped too.
Fuses to the fan are good. Supply voltages are good. My research has shown there are no relays involved in the fan control since PWM is used instead of high/low.

If anyone can help with this I will be forever grateful. I have spent hours researching this and haven't found a post with advice or a fix for this exact model and issue.
I'd rather stick a toothpick under my big toenail and kick a door than go to the dealer. Any advice or guidance y'all can offer is much appreciated.

[dzempel]

I've experience what sounds like the same issue with my 2008 535i. After being shown my a BMW tech how to correct an issue with my steering wheel, where the steering wheel would lower all the way down when I unlocked and opened the drivers side door, I decided to try a similar solution. I rotate the temperature control dial all the way counter clockwise and then all the way clockwise. It seems to me that this resets the system, at least temporarily. The solution for the steering wheel is to adjust it to its limits. According to the tech, this resets that part of the system. So now the first thing I do when something goes wonky it to adjust it to its limits. You never know.
Good luck.