Re: '06 MCSc with Auto Climate Control

I routinely turn ON the AC to check its operation as well as the radiator fan. Normally, about 5-7 seconds after depressing the AC button (snow flake) with the temp set at LO, the AC would kick in along with the radiator fan in low speed (Stage 1).

Well, none of the above showed any sign of life now. It was working fine, smoothly, cold with no noise or vibration. And then at only 37,350 miles, dead. Woohoo.... awesome engineering!!!

I've never had to work on the AC in all the cars I've owned previously. From browsing NAM, I've gained a some understanding but would like your help on diagnosing the AC.

1. Where do I get the tool to test refrigerant pressure? What are the pressure specifications? And should I test it with the engine cold or warm... or at what ambient temperature?

2. There is a AC relay in the fuse box. How do you test it?

3. The pressure sensor - how do you test it?

TIA...

 

I feel your pain. My A/C appears to have died @ ~50K miles.
Low speed fan died as well. Replaced fan, now low speed works, but doesn't turn on when A/C kicks in. My current assumption is that the compressor is not compressing. Per Bentley:
"low speed fan turns on when the AC is on and the AC system pressure reaches 8 bar (114psi)"

Would love the answer to your questions before I replace my compressor and drier, though.

 

Eric,

It's ironic that I have brand new Bentley manual in front of me and the section on the AC has only instructions for removal & installation of AC components. Absolutely zilch on testing, diagnosis, evacuation & recharge.... while the Bentley manual on my '01 VW Beetle has everything. I wonder if BMW has a say in what Bentley prints.

 

Could be as simple as low refrigerant. If it is too low the compressor won't come on, this protects the compressor from damage. You can get a gauge at most auto parts places.

 

Right. If refrigerant is low enough, the pressure sensor will prevent the AC compressor from being activated.

However, I need specs to rely on as to how much pressure is normal for both the low & high sides. Bentley for the Mini has nothing.

 

most any decent auto repair can slap on the pres' test unit and see if you have gas ... and if it is low they can recharge it while checking for leaks.

Nothing special about a MINI in this regard. A basic check usually runs me about $20 bucks plus a charge for the gas if you need it.

If you actually have leaks that's a different story ... but finding out won't cost much.

Now if you go this route they may well tell you there's a more serious problem then you actually have. I took my Honda to such a place last year and they told me I needed a new condensor for $$$$. But they were willing to just charge up the system and let me see how long it lasted. That was almost a year ago (yes, I'm in Florida and do use a/c at this time of the year). So I guess my leak is pretty small.....

 

When mine first went warm I just got some R134a (I miss freon ) in a kit with an integrated pressure gauge. It's simple, but effective. Seemed to help for a bit, but now I know it's full, and still nothing.

 

This is very complicated and there isn't any one correct answer it seems. Here is the problem as I understand it.

Power steering fan is often tied to low speed radiator fan.
Above fan can die with road debris stuck in it which will take out low speed fan.
If low speed fan doesn't work, AC will not come on.

What I can't find is a good way to trouble shoot without just changing parts.

It seems it can be the PS fan, the Rad fan, or your AC....any of these to make the AC not run...

I am going to let mini diagnose the issue then replace parts myself.

 

You're correct that the PS fan and radiator fan operate together. The signal is sent by the ECM to the relay (in the fuse box), which activates PS and radiator fans simultaneously. Both fans share the same fuse, which (in my case) is not blown. I've not yet checked the PS fan visually.

According to the Bentley manual... when the AC is activated, the radiator fan (Stage 1) comes on when system pressure reaches 8 BAR. When pressure is higher than 18 BAR, Stage 2 kicks in. At this point I'm not sure if the fan must come on for the AC to be activated.

This weekend, I will hot wire the fan and check the PS fan. If they both work, then the AC and/or refrigerant pressure and/or AC relay are possible culprits.