06 X5 e53 Auxiliary Fan Not Working with A/C on

[Auto Parts Guy]

So this is a wierd one for me. 2006 e53 M54 Automatic. The AC works great when cruising at highway speeds, ice cold. But the aux fan does not come on when you turn the AC on. The fan works, I've activated it via INPA several times on 2 occasions and works every time. But it will not turn on when the AC is on. Ive seen it on after coming back home from a drive but im not sure if that was bc of the coolant temp, or random/intermittent working as it should. What am i missing? Seems the DME has a good signal to the fan.. Has to be the signal from the compressor to the DME, right? Any ideas?

[White94RX]

Does the A/C work at normal speeds, and when stopped, idling? If so, I wouldn't worry about it. In my experience, the A/C being on doesn't always equal the aux fan has to be on.

[Auto Parts Guy]

The AC does work very well when cruising and so far seems to work at stop lights etc. I also checked the fan on 3 different occasions today and it was on, then turned off when i turned the AC is off. Ive also had my gauges on when i replaced the AC high pressure switch thinking maybe thats it. No schrader valve there or on e60s btw..

What made me think there is a problem, is it takes a minute or 2 for the AC to get cold when the car has been sitting, plus the fan does not come on immediately upon turning the air on. But maybe the aux fan is not supposed to come on every time the AC is on?, which is different than any other car I've ever owned.. I need to get the Bentley manual or check the AIR tool a little deeper.

[White94RX]

Have you had the refrigerant level checked? I mean recovered properly for measurement and recharged? Not just a shitty gauge on a can. A proper recovery and recharge is pretty much always the first step in diagnosing any AC issue. I really wouldn't worry too much about the aux fan. A minute or two of warm air could be an issue. It won't blow ice cold in the first ten seconds, but it should start cooling a little quicker than two minutes. When testing AC systems at work, I usually stick a thermometer in the dash vent and run if for about 2 minutes. I usually see the dash outlet temp reaching below 40 within two minutes, and close to 30 after a minute or two longer.

[Auto Parts Guy]

I haven't checked it like I should yet to be honest. I did replace the high pressure AC switch with a used one from a buddy's parts car thinking that was the problem, and when doing so, since theres no schrader valve, i lost a little refrigerant. So I re-charged the system with what i lost (about half a can). I have a professional AC gauge set. The only problem is, that night when i was recharging, it was about 50 degrees F outside. I prefer for it to be between 70&90 when I'm doing AC work, only personal preference. Pressures were around 27 & 160 ish. not great IMO. I want to see what that are on a 85 degree day. AC is ice cold when driving and when aux fan is on. (Seems to be working now, just doesnt come on immediately.)

So with that said, it could be that the high pressure switch was bad and the used one works, but I'm not even sure that switch is involved. My thought is maybe it needs to see let's say, more than 100psi before the fan kicks in. I know when you unplug that switch, the fan runs at full speed. I could also have a worn compressor, and this is the cause of my slow build up of cold air when pressures are static. Thoughts?

One other question. I'm trying to follow the logic behind an evac and refill of the refrigerant. What would be the problem that new refrigerant would fix? I guess contamination or something?
Thanks for the feedback!

[White94RX]

It's not an issue of "new" refrigerant. It's about measuring exactly how much was in the vehicle, adding a little oil/dye, and recharging to exactly the amount required for the vehicle. And seeing how well it does or doesn't perform.

I used to use gauges and cans to do AC work. You'd be surprised at how inaccurate it can be.

Sent from my Pixel XL using Tapatalk

[Auto Parts Guy]

Understood and thanks for the clarification.
I have a small update. So I think the AC high pressure switch that I swapped over from a buddy's e60 fixed the fan issue not coming on at all. It still takes a minute or 2 for the air to get cold. But once it does, it works the whole trip including stops. Fan has been on every time I checked. I conclude that the fan only turns on when the AC reaches a certain pressure at the switch. 2 things to note: no Schrader valve, so be quick and prepare to top it off. The fan should work at high speed if you unplug this switch.
I also hooked up my gauges. About 32psi on suction side and 225psi on the high side at 82* F ambient temp after a 20 min drive from work. Not that great, but I'm not going to do anything at the moment. I have plenty of other cars to drive if something happens. I conclude that I'll need a compressor in the near future. Hope this thread helps someone!

[Qsilver7]

Just an FYI (since I didn't see it mentioned)...the aux fan on the M54 operates when a PWM signal is sent by the ECU/DME...it doesn't come on just becuase the AC button was pressed like some older BMW models with the M50/M52/M60/M62 engines.

[Auto Parts Guy]

Yeah i saw that. I wonder what gives the DME the signal. I guess I'm used to my S52, M52, S62 and M50 engines.

So a little more info. The past few days, sometimes it will take 5-10 minutes for the air to get cold. Once it does, it does it immediately and stays cold the entire trip. If I only stop for a short amount of time, it will work perfectly right away. Ive read many other e53 owners have the same problem. Also if the engine is revved, that will sometimes trigger it to blow cold. I'm convinced I dont have an aux fan problem any longer. It works as it should. Other things to note, the pressures today were 40psi and 250psi on an 85ish ambient temp day. They took about an hour to equalize, but when they did, they settled around 95psi. One other thing to note. I had my gauges hooked up and started the AC when the engine was cold, noticed the compressor engaged, but zero change in pressures. Went for a drive and within a couple minutes it was working fine. Now I'm leaning towards an expansion valve problem.
I think I'll start as already suggested, by evacuating the system and recharging to 440g. Then I'll post back with results. Has to be refrigerant amount, compressor, or expansion valve..

[MauroGuzzi]

Hello Please I have the same problem. Did you find the iusse?