# AIR CON COMPRESSOR WOES - please help!



## TT_hunter (Nov 4, 2010)

I'm looking for advice about the air con in my 1.8T Quattro 180. The air con hasn't worked since I got the car, which was last November so it didn't matter. However, as we finally got some good weather in the UK this spring and again this summer, it has become more of an issue and one I wanted to get sorted.

I initially thought the aircon just needed gassing up, so went to Halfords and asked them to do the business. They tried, but the system was already fully pressurised. They suggested it was probably just blocked up from maybe standing for a while before I bought the car, and suggested I turn the system to LOW and force it to run for a week or two, then come back if it didn't clear. It didn't so I went back. They tried the pressures again and noted that the a/c compressor clutch didn't engage; this would need booking in with a garage to sort out.

When the service came due, last week, I booked the car in and asked them to investigate the aircon issue. I'm armed with an after-market warranty that would cover a replacement a/c compressor if needed. However, the garage advice the compressor was serviceable when jumpered but was only getting a 9v feed so they suspected an electrical wiring or system fault somewhere. They said I would need to go to an Audi dealer for a fuller diagnosis.

I went on Thursday. Audi charged me £200 (1.5 hours) to tell me what I already knew; the system is fully gassed, the compressor isn't kicking in, it's only getting a 9v feed. They added that the compressor might have 'broken up' in side and blocked the blowback valve; they would need 3 more hours (!) to investigate the wiring and then possibly need to replace the valve and the compressor at extra cost (on Audi rates).

Ouch! I've read every article on the forum about aircon in the hopes I might get a quicker/cheaper answer. So far, I've tried the "secret aircon codes" (press and hold the recirc button and press the manual flow control up arrow) - 1C showed "0.0" which apparently means "no malfunction present" in the system; I've tried removing, checking, cleaning and re-seating fuses 3, 5, 25 in the driver side fusebox (the only ones referred to in any air con details in Bentleys), and also did the same to the fuses in the box over the battery compartment, to improve the current feed to the a/c compressor; I've even tried jiggling the aircon "OFF" switch (in case "ON" wasn't fully engaged) and switching the "ECO" button to ensure it was fully disengaged too.

Any ideas anyone, please?


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## HIRAM (Feb 15, 2010)

If your vehicle is covered under warranty why are you out of pocket, its their responsibility under the 1977 sales of good act that the goods must be *fit for purpose*, ie air con is meant to to operate to the function it was manufactured to do, in your case it does not, read the small print if necessary get legal advise before you part with any more hard earned cash

to be honest sounds like a long costly investigation, I did mine and took 5 months of trial and error to get to the root cause which was more than one fault..mines was - low gas,f129 high pressure switch, electromagnetic clutch plus both fans. Every thing is fixable but at a cost the question is who pays ? ....quick fix drive with window down "summer" will be here and gone in no time..last year I went to the toilet and missed summer, but I stay in Glasgow area Scotland...If you stayed local to me I would loved to get my hands on this one, I love a challenge plus I work for free only pay for parts ....but thats just me

Rob

PS

OK I may have missed the the mark on this one slightly you may not be of the UK so legalities may differ from your part of the world, but cant see why it shouldn't ....but hey as my ex wife would say i'm not the sharpest tool in the box. However when I asked for more wood to finish a project she said "more wood" (not a porno quote..lol)it doesn't grow on trees you know....and she wasn't even blonde ..lol


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## TT_hunter (Nov 4, 2010)

Cheers HIRAM, thanks for your reply. I bought the warranty myself (it didn't come with the sale of the car) - but i take your point that the air con should hve been in working order when I bought it. Also good to hear your experience finding the fault; sounds like it may be worth me doing what I intended, and getting a local electrics expert on it, rather than part with silly money at the dealers.


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## Grahamstt (Jul 22, 2008)

Where about are you, if you can come to Chester area I'll look at it for you
[smiley=thumbsup.gif]


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## Typhhon (Oct 28, 2006)

Check fans operate. If not move to fan controller.
Does your engine run on pump work?

Blocked through standing.....duhhhhh! where do they get this stuff.... a block of the expansion valve normally occurs from poor repair practice (cleanliness, air and water left in) and or the use of dirty equipment.

A 12v live feed to the compressor clutch will tell the story but only for a few seconds please.
Should hear a healthy clunk.

The clutch relay is a bit feeble on the TT (same as the A3) and knwon to fail but it sounds like something down stream and electrical to me.

P.S. Pressure means little other than the LP switch that prevents dry running is activated. R134a is a phase change fluid so you only go low pressure when its almost empty. The only way to know if you have the correct refrigerant level is take it all out and then weight it in. Should be 0.775kg R134a and 135g of oil.


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## qs950 (Apr 12, 2009)

> Also good to hear your experience finding the fault; sounds like it may be worth me doing what I intended, and getting a local electrics expert on it, rather than part with silly money at the dealers.


Had an air con compressor fail diagnosed at the TT Shop a few years back and although a big bill [ I've sold the car and the service history went with it] to replace it IIRC came in under £500 [it is a pricey part - was told to sit down before they quoted]. Give them a ring - I always find them helpful on the 'phone - what have you got to lose and your warranty should cover the cost?


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## Grahamstt (Jul 22, 2008)

Grahamstt said:


> Where about are you, if you can come to Chester area I'll look at it for you
> [smiley=thumbsup.gif]


Bump

We have full a/c facilities and equipment


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## landwomble (Feb 9, 2011)

Grahamstt said:


> Grahamstt said:
> 
> 
> > Where about are you, if you can come to Chester area I'll look at it for you
> ...


I'm not sure what's going on with mine, and I work in Chester fairly regularly - no symptoms other than it's not going cold any more...! Fancy taking a look at mine?


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## Grahamstt (Jul 22, 2008)

landwomble said:


> Grahamstt said:
> 
> 
> > Grahamstt said:
> ...


Not a problem, we can do a quick healthcheck on the system, just PM me when you think you can come
We're actually in Sandycroft near Queensferry


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## landwomble (Feb 9, 2011)

Even closer! I work some days in Ewloe with Unilever...


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## TT_hunter (Nov 4, 2010)

Hi, a further update on my air-con woes.

I took the car to an auto-electrician, who spent a day on it for free (respect to him for that) but couldn't find the reason. The compressor will run when jumpered, so that's not it. He couldn't find a wiring issue anywhere. The system seems to be de-activated. He didn't have the means to check whether high pressure was driving a cut-off of the compressor clutch.

I'd love to be able to check the air-con channel codes which have received a few mentions on here (as I believe they feedback any air-compressor-off switch statuses). However, the codes as published on the forum so far don't seem to match my TT. If anyone has a correct listing for a 2000 1.8T, I'd appreciate that 

So, is it (a) a controller, (b) a switch or sensor, (c) a combination of issues?

Please, someone, save me from the stealers (they've cost £200 so far and quoted £400 more, just to look at it). Any ideas how I go about locating the issue (now I know it ISN'T that the system needs re-gassing, the wiring or fuses/relays are bust, or the compressor is seized), and then how I can fix it?


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## HIRAM (Feb 15, 2010)

TT_hunter said:


> The compressor will run when jumpered,


 :?

Hi TT_HUNTER

How did you jump the electromagnetic clutch, was it as below?

connecting terminals 1 & 2 should activate the electromagnetic clutch as per illustration below

connecting terminals 3 & 4 should activate the fans as per illustration below

the "A" is the pressure switch

If the pressure switch is faulty ie stuck in the "OFF" position the clutch and the fans will not operate,but if you jump them with the terminal "B" connection they will work

If the "activator" that the switch screws into is defective it wont work either......

You can "safely" unscrew the "A" pressure switch without depressurization of the air con system so there must be some sort of valve/plunger to activate the switch,was this checked

I'm sure someone with more knowledge will put you on the right track :wink:

Rob


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## Typhhon (Oct 28, 2006)

If your compressor runs and the pressure switch is 'engaged' next is the J293 Radiator Fan Control Unit.
If that goes you can loose both fans and the run on pump. No fans no A/C
Check fans work the fan motors are reported as a bit of a VAG issue.
A VAG COM scan may show the issues?
Checked all the fuses?

http://www.wak-tt.com/guides/ttc.pdf page 78 onwards may help....


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## TT_hunter (Nov 4, 2010)

The pressure switch in the picture (thans for the post, by the way) isn't a match for the one on my car. It has a box-shaped black plastic cap end with three contacts to correspond to the three contact plug on the wiring. The switch is off a j-bend junction from the A/C pipework, against the bulkhead of the engine bay, behind the engine and was covered by a heat-reflective pouch which meant I initially couldn't find it. The replacement unit I got from Audi is a different shape again (latest variant, I think) with three contacts inside a box-shaped black plastic plug and a hexagonal aluminium screw-thread valve end; but it looks like it will swap out with the original. I'm frankly a bit terrified of trying to unbolt the sensor though, as the potential to crack the pipework at the j-joint when doing this seems pretty high to me. Any advice on how to do that would be a real benefit. Do yuo just use brute force or is there a special knack (and why doesn't Bentley tell you this stuff?)

After trying another "specialist" garage that said the fault was with the A/C compressor itself, and getting it swapped out only to find it wasn't, I'm left with the following potential causes, I think.

It could be the high pressure sensor (if I can succeed in swapping that out then I can rule that out); it could be the wiring to that sensor, which looked more than a bit fragile to me; it can't be the A/C compressor or clutch (because there's a brand new one on there now); it could be a wiring short (the aircon codes NOW tell me 15.4 which apparently equates to a sporadic short on the airflow flap potentiometer); it could be 'something else' including the A/C head unit maybe?


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## TT_hunter (Nov 4, 2010)

Also, to answer various suggestions, the blower fan etc. all runs fine. The only issue is that the a/c compressor doesn't run.


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## TT_hunter (Nov 4, 2010)

In case it helps, the final cause turned out to be the ECU. It had been replaced by the prior owner (I had no idea) and the replacement was faulty. It wasn't sending engine revs so the a/c control unit thought the engine was switched off and would not send a switch on command to the compressor. Hope that saves someone else the £2.2k it cost me to gain this wisdom from the dealers.


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## mauvedipstick15 (Jan 25, 2011)

Glad you got to the bottom of the problem,albeit an expensive and frustrating journey for you.


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## t'mill (Jul 31, 2012)

How did it jump from £400 for Audi to further investigate to over 2k?  
I'm genuinely worried about the cost of running these cars now!


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## HIRAM (Feb 15, 2010)

*Wow*,I would have never of guessed that one [smiley=book2.gif] . I wouldn't be surprised if you were the only person in the world that has ever had that fault. I would like to say a sincere thanks for completing the post and telling us the final out come as so many posts on here do not conclude. Hope that you have trouble free time now

Rob


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## apj (May 31, 2012)

TT Hunter my sympathies, this seems to be part of TT ownership or in fact ownership of ageing modern cars with dealers wanting £140 plus an hour and the challenge of finding the cash and a good indie.

My air con doesn't work either I did the same as you spent cash regassing it, failed, to be told by a garage that the compressor clutch was not engaging so the compressor and clutch maybe knackered. Thats as far as I have got as the money ran out.


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