Help with diagnosing broken AC

[J400uk]

So its that time of year again where the hot weather starts and you realise that your AC no longer works

I've just got back from Kwik Fit where I went to have a regas done but I was told the Compressor is buggered, as apparently although the gas was low recharging it didn't make a difference. Have since done a VCDS scan and under Auto-HVAC the following error is showing:

1 Fault Found:

00229 - Refrigerant Pressure
            002 -- Lower Limit Exceeded


Also had a go looking at the measuring blocks which showed the following:



My question is, was the Kwik Fit diagnosis of failed compressor correct? The reason I'm suspicious is the VCDS "Compressor Shut-Off Code" of 3 would seem to indicate that the reason its not running is "pressure in refrigerant circuit is too low". I've read elsewhere it might just be a switch/ sensor that's gone. I rang VW UK for a laugh who were as unhelpful as ever denying its a common problem, along with the corroded wings I also noticed this week...

Any suggestions appreciated 

[stealthwolf]

I had my aircon recharged last year. The chap told me the compressor in VAG cars is different as it tends to be on all the time. There is always some gas leaking and over time this can accumulate into a significant loss by which time there's too little gas. It's akin to too little oil in the engine. Your car is older than mine. Have you ever had the gas topped up? If it's truly buggered you're looking at £1k for a replacement.

[J400uk]

I had my aircon recharged last year. The chap told me the compressor in VAG cars is different as it tends to be on all the time. There is always some gas leaking and over time this can accumulate into a significant loss by which time there's too little gas. It's akin to too little oil in the engine. Your car is older than mine. Have you ever had the gas topped up? If it's truly buggered you're looking at £1k for a replacement.

Don't think its ever had any work done on the AC before as I've looked through all the invoices from the previous owner and nothing is mentioned. Bit annoying as when I bought it a couple of months ago I specifically asked the seller if it was working. And yeah I've seen a few posts mentioning £1k compressor replacements, crazy expensive as that's pretty much 20% of the cars value!

[Viking]

Ross Tech Wiki seems to think that the low refrigerant pressure is the fault, not a compressor issue. Link.

Also, kwik fit? They have trouble fitting tyres the right way round, never mind discharging and refilling air con systems. 

[Baz300]

VW are doing a summer health check for £25 which includes checking the air con

http://www.volkswagen.co.uk/owners/summer-check

I don't think they charge too much for a top up either

[omeydz]

Hmm.. I had new compressor and condensing radiator on my MK5 which was done under warrenty not long after I bought it.

The compressor had a distinct louder than normal whining sound that was linked to revs which i noticed from inside the car ( told its compressor internals disintegrating and metal shavings clogging the system so had that changed and AC system cleaned through).

Later my AC gas escaped and I only got the refrigerant low fault code. Compressor refuses to cut in also ( so it doesnt get damaged?) .. Dealers regassed and it escaped in 24hrs. They then regassed with a UV tracer which found a pinhole in the condensing radiator which was swapped out and a stone guard added for protection from the road.

So back to your story and enough of my past troubles.. You need gas for the compressor to kick in.

If you regas and the gas stays in and compressor kicks in and you get cold AC then jobs a good'n

IF you regas and gas stays in and compressor isnt working (faulty compressor or pressure switch/sensor) or sounding rough (failing compressor).

If you regas and lose gas quickly, but compressor works fine briefly with none of the above issues you have a leak in the system... Get a UV tracer pumped in with regas and use a uv lamp to examine all of system components and parts.

Its a long winded process but methodical and will help pinpoint the issue and not spend ££ unnecessarily!

Hope that lil essay helps you 

[J400uk]

Thanks guys. I think I'll first try and get the pressure switch/sensor replaced and go somewhere that knows what they are doing for another regas. Fingers crossed that fixes it!

[Baz300]

no one should be gassing up the system until it has been checked for leaks with an inert gas and dye especially if the system is known to have leaked out at some point.

Air con gas is VERY harmful to the environment and yourself .

[Sdw172]

Mine was leaking and it turned out to be the condenser

[J400uk]

So I bought the new pressure switch and had been planning on fitting it myself and having another regas done, but am having a bit of a nightmare getting it installed. There is very little access space to reach down and certainly not room for a spanner. I also took it to a local garage who initially thought it would be a 5 minute job to change but then decided it would be 1 - 1h30 in labour because they wanted to remove the front.

Not sure what to do nowas its looking like the pressure switch is going to be a lot of work to fit and theres a risk it might not even fix it. Is it worth just biting the bullet and changing that at the same time as the compressor (and another regas)? Otherwise just feels like a gamble 

[J400uk]

Oh and just for clarity the system is currently de-gassed, nothing in there at all so perfectly safe. Climatronic is surprisingly effective even without AC otherwise I think it'd have driven me mad by now!

[rich83]

You need a crow foot spanner!! 

[Pikey Motorsports]

I got a compressor laying about for sake if you need one

[J400uk]

Yeah might be interested if you could PM me over the details Pikey Motorsports.

@ richwig83 - haha that's the same as what my mechanic friends told me, trying to find somewhere to buy one

Shame there doesn't seem to be a way to tell whether the cars needs a new compressor or the pressure switch/ sensor without changing one!

[simonp]

My switch broke and VW charged me around £230 to diagnose, replace and re-gas. Felt a little ripped off that they didn't supply the switch for free, as it's a known common fault.