Mark 5 2.0 TDI (2008) Air con issue

[harlie]

Same problems and I tried the same thing. New TX valve installed, worked for 15 mins then nothing as it was clogged again. While this does work for some poeple, the source of what is clogging the valve in the first place has not been fixed. AC systems don't just clog up. They are a sealed system that should not lose pressure, or have anything apart from the compressor oil and R134. If the TX vavle is sticking, something has entered the system to do so, and 99.9 it will be the compressor failing sending swarf through the lines.

That said, if you catch it early enough a simpled replacement of the vavle will help, but not fix the issue long term.

the RCV valve is not the same as the TX valve - one is in the compressor controlling compressor output levels (electrically operated and prone to sticking) , the other is inside the cabin before the evaporator acting as a pressure regulator allowing the refrigerant to expand from a liquid to a gas (pressure operated and not prone to sticking but can block up).

RCV = Refrigerant Control Valve
TX = Thermal Expansion

If your TX valve is clogged, that is very different - did you see it? Was it really clogged? I bet it wasn't it just wasn't the problem. You have said you fixed the issue with a new compressor - which means you got a new RCV (it's in the back of the compressor - where the wire plugs in) - So I'm going to stand by my research - you fixed it with a new RCV, the rest of the compressor came for fun.

Do a search for "delayed Air conditioning"on tdiforums, there are hundreds of posts of successful long term RCV valve replacements, the Sanden PXE16 compressors generally don't self destruct like the older Densos, but the RCV is proven to be not reliable. It is a very easy job in the US as R134A can be purchased from the local shop for $11-$12, with a set of $60 gauges they can DIY refrigerant recharge.

Delayed Air Conditioning - Page 32 - TDIClub Forums - BTW the guy on page 32 in Brisbane is not me it cost me 40 for the RCV and 100 to recover and recharge - so it looks like another BNE bloke has had a win. with the car on a hoist it took 3 minutes to change the valve. My valve has a very fine sludgy muck in the filter, there are no metal fragments. Educated guess I would say the muck is oil that's too old and been too hot.

There is a fine mesh filter on the RCV, metal swarf would not get in - However I do agree, if there are metal fragments then you have a compressor internal failure. But that also brings another Question - have you seen a cross section of the Condensor? How does metal swarf get from the compressor to the TX valve, the condenser has galleries that are 1mm in size.

As I said above, with VCDS it is easy to see if the RCV is the issue, a clogged TX would have given very different reading than a sticky RCV. A buggered compressor will give different readings as well.

[DWBN]

Perhaps that is where the confusion is - is the below the TX or RCV? I've changed the vavle in the compressor (which I thought was the TX valve) but with no luck. No swarf in the system either. Weird as it was working flawlessly for the first 30 mins after the swap and regass, then nothing.

[harlie]

That is the RCV - it is possible to get a faulty RCV - they are an electrical item.

If it worked after RCV replacement (if it changed the behavior), I still say the compressor was OK. If the compressor has gone, it doesn't come back temporarily - they fail because the wash board mech breaks, piston rings loose seal, pistons break, conrods break ect - when the compressor fails internally it is a doosy. The Variable output compressors are quite intricate inside (7 pistons!!), but the Sanden units are proving very good.

Next time - and I'm of the opinion there will be a next time it plays up because these valves are a serious week link. Start with your laptop and VCDS to see exactly what the ECU is asking for and what is happening. I have ordered a spare to have on hand when it does go....

[jets]

If you are interested I can post up exactly how to tell if your valve is the problem – you need VCDS and about 5 minutes. It will also help if you identify which compressor you have

I would be interested in this harlie.[I have VCDS] I am not sure if mine is slow to cool as my wife has been using it. I will try it next time I am in it.
Mine is a Sanden compressor. Nos on it 8676f, PXE16,04411809563 & 1KO 8508030. I used a mirror with a remote tilting head.
This means everything is reverse image.

[xradioactiveman]

Hi Harlie , can you tell me where you sourced your RCV from.

[DWBN]

Update: New compressor arrived and fitted. Changing the RCV valve didn't work for me, so this was the next option. I had M&J Auto in Merrylands do the work and am really happy with the result. Cost $270 fitted, which included the labour to fit the new compressor and a re-gas.

I had the sanden model too. As it turns out, I accidentally purchased two compressors, so now have a brand new spare. If anyone wants it let me know, suit mk5. I'll leave it here for a few days before posting in the fs thread as I know a few of you may want dibs? Cost me $350 landed.

[R36VW]

I have a MY10.5 R36 48k kms that the dealer just replaced my RCV on after I diagnosed and ordered the part from polarbear in the US. Mines a pxe16 Sanden. I had intermittent to no cooling and only 9-11bar in VCDS no matter what the temperature or load. The service guys were sceptical but it worked straightaway after an evacuation, RCV change and regas. Vent temp was at best 17c previously but is now back down to around 4c with no delay on cooling. There was a small amount of swarf and muck on the old RCV filter so it may play up again in the future at which time I'll do a full warranty job on it.

[jets]

Just to add a bit more info to this thread. In the Australian Auto Motive trade magazine [Oct '13] a question was asked in relation to a VE Commodore about not being allowed to start the engine when there is no gas in the system.
" The VE Commodore uses a clutchless air conditioning compressor, which can be damaged, or even seize, if run without a full refrigerant charge" -------"compressors rely on the flow of refrigerant to circulate the lubricating oil. Without any refrigerant, running the engine could cause irreparable damage to the compressor. To stop these vehicles being completely immobilised they have been designed to be able to be moved around without damage. The general guidelines are that you can drive the vehicle as long as:
*Engine speed is kept below 2000rpm.
*Is run for less than 15 minutes, and
*The air conditioning is switched off.
The Commodore is fitted with a Delphi unit. I guess the above instructions may also apply to the Sanden, Denso etc compressors fitted to our cars.
In an advert. for an information night on the Variable Displacement Compressors in the Automotive Engineer [July/August '14]
"These little understood compressors are now at the heart of most automotive air conditioning systems." So as VW owners we are not alone with these problems.