Air con fault diagnosis - help requested

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wonderloaf
Joined: Mon 02 Aug, 2010 21:55
Posts: 490

  Z3 roadster 2.2i
Location: Basingstoke

Air con fault diagnosis - help requested

Post by wonderloaf » Thu 11 May, 2017 12:48

Hi All, a couple of months ago I noticed that the aircon on my car (2001 Z3 2.2) had stopped working, so thought I'd try and get it fixed before the summer months are upon us.
As far as I can remember it was working one day and not the next although I used it so infrequently I can't be sure, and when I say it's not working it's 100% not working, no reduction in temperature at all. What I have noticed is that when the blower is at maximum and the aircon is switched on the clutch on the compressor doesn't engage so assuming that it is something to do with the functioning of compressor, wiring, fuses, relays, etc and not down to the refrigerant .. but I could be wrong!

So far my fault diagnosis is as follows:
1. Checked the AC switch function - assumed OK as it lights up orange and I can hear a fan going on and off behind the dash/bulkhead as I turn the switch on/off. Blower is turned off here BTW.
2. Checked the fuses - all OK. Checked the fuse numbers shown in the fuse box plus a few more for other models I found after a bit of digging around on the 'net, just in case! Used a multimeter to check.
3. Checked the relay - assumed OK as when swapped with the other yellow relay beside it the AC still doesn't work, so unless both are faulty (highly unlikely?) assuming the problem isn't down to the relay.
4. Checked the supply to the compressor itself - pulled the single wire connector off the compressor and used the multimeter to check if there was any voltage/current being supplied by connecting the meter between the single contact and ground - result was 0V/0A so assuming the compressor isn't getting a power supply and this is where the problem lies.

My next thought is to buzz out the wiring between the relay and the compressor, if this is OK then I guess I'll need to gradually work my way back to the switch, can anybody see a problem with this, are there any other components I can check easily to try and narrow the problem down?

Thanks in advance, Wonderloaf.
2001 Titan Silver 2.2 Sport
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BladeRunner919
Joined: Fri 17 Feb, 2012 20:18
Posts: 2221

  Z3 roadster 1.9

Re: Air con fault diagnosis - help requested

Post by BladeRunner919 » Thu 11 May, 2017 12:56

The most likely problem is that it needs a regas. If the pressure is too low then the system won't engage. I'd definitely start with that.

Howard Adams
Joined: Mon 10 Oct, 2016 16:39
Posts: 44

  Z3 roadster 3.0i

Re: Air con fault diagnosis - help requested

Post by Howard Adams » Thu 11 May, 2017 13:03

Most aircon faults are présure related. If the car is low on gas the clutch on the pump/motor won't cut in. Aircon systems often need a regas after 3 or 4 years.
My Z3 (3.0i) also doesn't work, so I will get a regas and then worry about it if it doesn't work.
Good luck

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wonderloaf
Joined: Mon 02 Aug, 2010 21:55
Posts: 490

  Z3 roadster 2.2i
Location: Basingstoke

Re: Air con fault diagnosis - help requested

Post by wonderloaf » Thu 11 May, 2017 13:11

Hi Guys, low or no gas pressure did pass my mind as being the problem but from what I'm seeing there isn't even any juice getting to the compressor so assume this may also be part or all of the problem.
A regas is on the cards but at the moment I've got a shedload of other things to fix before the next MOT so am trying to keep the spending down on non-essentials (which AC is in my book, but a nice to have!).
2001 Titan Silver 2.2 Sport
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BladeRunner919
Joined: Fri 17 Feb, 2012 20:18
Posts: 2221

  Z3 roadster 1.9

Re: Air con fault diagnosis - help requested

Post by BladeRunner919 » Thu 11 May, 2017 13:18

You won't get any power to the compressor if you are low on pressure. If you really want to be sure, then beirfly jumper the pressure switch to see if the compressor kicks in.

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wonderloaf
Joined: Mon 02 Aug, 2010 21:55
Posts: 490

  Z3 roadster 2.2i
Location: Basingstoke

Re: Air con fault diagnosis - help requested

Post by wonderloaf » Thu 11 May, 2017 13:21

BladeRunner919 wrote:You won't get any power to the compressor if you are low on pressure. If you really want to be sure, then beirfly jumper the pressure switch to see if the compressor kicks in.
OK didn't realise this, thanks for clarifying. Looks like a regas then!
2001 Titan Silver 2.2 Sport
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