Aircon Problems - Not always cold, temperamental, long to kick in and then drops out

[Pussbak]

I have a 2009 R36 and it takes 5-7 minutes for the air to kick in. Doesn't matter if its been in the garage all day or out all night. Once it comes in its cold as and will stay cold.
In trouble shooting I have turned the car on and let idle then monitored the AC lines in the engine bay. When the larger line gets cold the air is cold but it does take 5-7 minutes.
This is the same for warm air also.
Its really annoying since you need conditioned air for demisting the windscreen and so frustrating sitting on the road side waiting for the AC to kick in.

Im guessing the compressor is OK since once it kicks in it's fine.
Perhaps low on gas or a pressure switch failure.
It's not an intermittent fault but happens every time i start the car after its been sitting for more than say 1 hour.

Any feedback is welcomed and appreciated... Cheers

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[arcadelt]

Im guessing the compressor is OK since once it kicks in it's fine.

Don’t take anything for granted.

Any feedback is welcomed and appreciated...

Go and see an air conditioning specialist sooner rather later. See my post above for the reason why - don’t be that guy!

[Pussbak]

Don’t take anything for granted.



Go and see an air conditioning specialist sooner rather later. See my post above for the reason why - don’t be that guy!

Thanks arcadelt for the reply.
The hunt begins for a GOOD AC guy, someone that has experience with the VDubs and wont just tell me to regas it and see what happens.

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[s900t8v]

I'm a saab guy but have been working on a vw. Usually the main cause for compressor failure is low refrigerant. The oil needs adequate refrigerant volume to circulate and there is a slight cooling effect of the working parts of the compressor by the refrigerant that has changed state after going through your evaporator. The way to determine if your refrigerant is low is usually by checking the sight glass. Or alternatively watching to see if the compressor clutch is engaged from the moment you turn on the switch in the cabin.

If the compressor clutch is engaged and you aren't getting cold air straight away it could be a few problems the most common is low charge. Or a sticking thermostatic expansion valve I've just rebuilt and regassed my own ac in my 84 saab with hychill so have a fair understanding of the setup. That being said there are lots of faulty signals that can prevent ac from working . Like full throttle deactivation. Engine heat deactivation. High pressure deactivation or low pressure deactivation. You can tell if these are working if you're seeing your ac compressor cycle on and off rapidly or not cycle on at all.

I don't have much faith in genuine diagnoses by ac guys. Good money is to be made in Aus by ac guys given the voodoo status it has. But it's really pretty simple system to trouble shoot. Provided you don't have a leak of oil there's no harm in trying an evacuation and Regas. And most of the time it's just because the hoses and o rings leak a small amount of refrigerant over the years as the materials degrade.

[Passat my07]

The problem is these cars don't have a compressor clutch. They are a variable stroke compressor. The solenoid valve can fail so they won't alter the stroke.
The compressors also don't mind destroying themselves and filling the system with metal. That's probably why the pros prefer to just fit a new compressor and be done with it.

[arcadelt]

The compressors also don't mind destroying themselves and filling the system with metal. That's probably why the pros prefer to just fit a new compressor and be done with it.

^^ this ^^

[Pussbak]

Thanks to arcadelt , s9008v and Passat my07 all for your replies.
I had the car checked out today and the diagnosis was a faulty valve within the compressor which was not serviceable and was advised that a complete compressor replacement was required.
Upon further digging I found some useful info here so might give this a go.


Secret air conditioning sequence? R36 2008

[Passat my07]

You should be able to get the valve if you look around. You need to know which compressor you have though.

[Pussbak]

Extremely happy to report that the control valve was the culprit.
Comp (Sanden PXE16) is ok and system was tested leakfree
Air temp at the vents is now 3°C and BING BING on the nipple meter.
Thanks again to all that responded.

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