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Discussion Starter #1
Guys, I currently have no ice-cold aircon. When I turn on the aircon, the button lights up, but temperature of air from vents does not change at all. All other heating/ventilation controls and adjustment appears to work exactly as it should with no erratic fan speed or other problems normally associated with final stage resistor unit. Am I correct in assuming that this is unlikely to be a final stage resistor problem, or could a problem here present itself only with lack of aircon, but all other heating controls working perfectly.

The auxilliary fan does not come on when aircon is switched on, but I know it does work as a) I have replaced this (due to unrelated cooling problem issues), and b) I have heard and seen this fan operating.

I have had aircon topped up last summer, although if I have a leak, I am sure this would need redone.

I would like to look at this, at least initially, from a DIY point of view. My first inclination is to buy a regassing canister of R134a refrigerant and top-up. My question is, based on what I have said, is this likely to be the problem. I mean, if there is insufficient gas in aircon system, would this cause auxilliary fan not to come on when switching aircon on. Obviously I could be looking at other specific aircon components which would be beyond my ability, but don't want to hand over to specialist if this could be a relatively simple repair.

Any advice appreciated.
 

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Easiest thing I would try first is sit there with it idling and turn the air-con on, if the revs drop even ever so slightly, I think I'm right in saying that would be the compressor kicking in.

I had my air-con serviced at an indy recently as I would never have the tools and equipment, or knowledge, to test it. Somewhere so-equipped can test for leaks with a dye, and recharge it all. Cost me about £50 but now I know all the little leaks that it had are all sorted and come summer, I can complain about it being cold again ;)

Now I just need to stop it from blowing full heat for random reasons...lol
 

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Discussion Starter #4 (Edited)
Guys, the revs aren't dropping when I turn on a/c. The engine is cold, however and this might be something that is more noticeable when engine is up to temp. One thing I do notice is that when I turn a/c on, there is some kind of audible movement, perhaps ventilation flaps (although I am guessing here), and a subtle change in hvac noise/tone.

Another point that I hadn't thought of previously was the nature of the work I had carried out on the car just before I noticed this problem occurred. I had guide rails, timing chain, chain tensioners, thermostat, aux fan, water pump and steering box all replaced in last year (I know, huge maintenance bills indeed!). Would the nature of any of this work result in perhaps removal of vital a/c related parts that would mean a top-up would not only be advisable, but essential?

Feeblebob - random hot air - have you checked final stage resistor (hedgehog)?
 

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You need to check the refrigerant pressure (the low pressure port) - this is easy to do and you can get an inexpensive gauge from any auto parts store.
 

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Low pressure switch. If you have low pressure there is a switch that shuts things down so you do not burn out the compressor. Sometimes these little beggers fail on there own. Not sure where it is on these cars but I am sure realoem will have a pic.Sounds like you have one of the two. If you are going to DIY a refill get the kit with the gauge. There is also a cannister for the same system that is a leak stopper. Leak stopper is a working fix for small leaks but useless for fast leaks.
 

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Now I just need to stop it from blowing full heat for random reasons...lol
This is most likely the Heater Solenoid Valves located in the engine bay on the passenger side wheel arch.....

Mr Chilli :

Weird stuff....

I also switched on my AC today.
I also noticed it wasn't cold
I also regassed my system last summer

Was your ambient Temp Readout showing less than 10 Deg C ? I am pretty sure when this value is low, the AC simply will not work even if you switch it on and the AC system is healthy.

Easy solution, take it to an AC specialist. Who will leak test with dye as stated by feeble.

If your compressor is working and the electric fan is working (although you should blow cool cabin air even if this isn't working for some time until the engine heats up alot iirc) then it could be simply a leak, but lets hope its not leaking from the condenser lets say..., but rather an O Ring somewhere in the system, thats also easiy accessibe.

Good Luck
 
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Discussion Starter #8 (Edited)
Was your ambient Temp Readout showing less than 10 Deg C ? I am pretty sure when this value is low, the AC simply will not work even if you switch it on and the AC system is healthy.

Ambient temp was indeed below 10C here today. You are saying that aircon system in our cars doesn't function when ambient temperature (as measured by temperature sensor in driver-side underbody part at front bumper?) is 10C degrees or less. Can't believe I didn't notice this before, but if that's the case, I guess I might be fortunate enough to not have to do anything but wait until it heats up a couple of degrees here in Belfast. Might be a while though...I'll monitor this for next couple of days just to make sure this isn't the reason.
 

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Go put a cigarette lighter under your ambient temp sensor for a bit, and then switch on your AC.....:) Ha ha only kidding.

Another weird point is, if you unplug your temp sensor, and then the wiring connector gets wet, the ambient temp readout shows some wacky values and your AC doesn't work either....ask me how I know !

"how do you know ?"

Because I had my temp sensor unplugged and then got my car washed, and then had no AC in 30 Deg C and ambient readout of sub zero...

Anyway lets see what happens with your AC when ambients warm up a bit more.

Good Luck
 

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Hi,

I think it ambient +5C before the AC works.

Hit the Max button when its +5C outside and see what happens.

Also just to be sure (i'm sure you've done this), that your dial (number 3 below) is set to cold.
 

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Never occurred to me that when the ambient temp is low, the air-con system itself doesn't kick in. Same with my old car actually, now I think about it.

And on my hot air issue (no sniggering at the back...), yes, I think it's looking like the heater solenoids, been building up DIY's and prices for the part over the past few weeks, cheers all.
 

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I just wanted to say an enormous thank you to contributors to this thread, especially M5 London and phump! You guys have just saved me about 350 pounds in unnecessary parts and labour. Garage and I were convinced air con fan on my car had broken and it had been booked in for a replacement to be fitted next week. Turns out as was stated here, that the fan just does not come on if the amb temp is <5. By coincidence it was <5 when I did my normal monthly winter a/c running for a few mins to keep the system going a couple of weeks ago and when it went in to the garage yesterday for an inspection. Thought i'd consult this forum "just in case" there was some quirk to check and so glad I did! Surprised the garage did not know about this as it is a BMW indy specialist and in the past they have been good with most things on the car. But anyway, this thread has just made me very happy so thank you all again!
 

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Discussion Starter #13
Thanks to all who replied. After checking this on a surprisingly hot Wednesday here (16 degrees C in Belfast!!), I can confirm that my problem is not ambient temperature related. I have arranged to have this looked at by air-con specialist next week, and will report back with his findings.

Thanks again guys.
 

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A cheap check is to check the 134a pressure. The system is a closed system. If the pressure reading is low, then you have a leak. If the pressure reading is normal, then it's a mechanical issue.

Hope everything works out and it's not an expensive fix.
 

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Discussion Starter #15
Quick update - finally got round to leaving the car with air con specialist today. He says that the system was completely empty. Apparently on systems that require a top-up there would generally be some amount of gas remaining, but in my car there was none at all. He tested, cleaned and regassed the system. Cost was £80 and took just over an hour total to complete. I now have a rediculously cool cabin once again! I am assuming that the nature of work completed over the past year (timing chain & guide rails, water pump & t-stat among others) meant that the system got drained of whatever gas it contained. Relieved that it was just a regas, and not in need of air-con related replacement parts/labour.

As always, a big thanks to all who offered their advice.
 
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