a/c taking time to start cool; advice needed with tech
 

I hope someone will have some guidance for this issue.

The a/c blows warm air for some time after startup when driving for a few miles.
And then the fan kicks in and the a/c starts to cool.

The a/c only works well when driving at higher speeds and worked ice cool on a recent 4 hour trip. However, at low speeds, it doesn’t cool as good. The fan seems to respond (when setting the a/c to max) but it doesn’t start for some time after initial driving from a cold engine.

The tech has checked:
a/c pressure line was good
Freon extracted and replaced
Heater and everything else is working fine.


The tech wants to replace the a/c control unit (even though it’s not reporting a fault code).
Is replacing the a/c control unit (without a fault code) a logical next step?
Any advice would be appreciated.

Hi dude: I had a similar issue. The problem is the compressor. It has an internal leak and condensation . So the clutch will not engage until that condensed freon gets evaporated. It is a safety feature. The only solution after a month of troubleshooting and research was to replace the compressor.
Greetings

There is also a pressure sensor on the A/C line. That will prevent the fan from running immediately as it should when you turn the A/C on. For example, if the car is cooled down, like overnight, and you start the car and turn on the A/C, the aux fan should run immediately.

Thanks for the replies.

I’ve read in posts for SLOW COOLING AC problems:
Replace compressor (although dealer told me that compressors either WORK or DON’T WORK; others have indicated that compressors can have DEGRADATION over time)
Check Compressor clutch
Check sensors
Check final stage (for incorrect fan speeds)
Dealer suggested replacing the AC CONTROL MODULE (but it doesn’t have FAULTS or show other signs of problems)

My problem is that the auxiliary fan doesn’t start right away but does start eventually.

It does cool (not that great though) eventually but very slow to do so. Also, the ac warms up when in traffic or coming to a stop.

On a recent long trip, the ac was ICE COLD and I adjusted the temperature to 78 because it was so cold. Usually I set the temperature at 70.

So the problem is definitely a SLOW TO COOL problem.
From reading other posts, it seems the AC CONTROL MODULE would be the last thing to replace. This is why it's confusing the dealer wants to replace that first (even though it does NOT have a FAULT CODE)

The A/C compressors in our e60s is of variable displacement design. There is no clutch to cycle on and off, the compressor runs all the time. Slosh plates internal to the compressor are adjusted by means of a solenoid valve assy to varry the capacity of the compressor. This valve assembly has been known to act sluggishly on some units. In my case the compressor was changed out twice over the course of the original warranty. BMW doesn't replace the valve assembly, they replace entire compressor. I've been lucky, it's been 6+ years sense the 2nd compressor and all remains good.

There is a thread in bimmerfest.com that covers this solenoid valve assembly, it's 15-16 page long thread. Not saying this is your problem, but it surely sounds like it. The thread was active in last couple of weeks.

Good luck!

So, the problem is now fixed.
1) Compressor replaced
2) 2 a/c lines replaced (reported as leaking). I noticed there are sensors or an electrical connection in 1 of these lines.

I’ve noticed the auxiliary fax now starts after a few seconds. The a/c air reaches cold temp very quickly. The a/c control module was working properly and was not replaced.