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Air Conditioning Leaks

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Hi Guys, need to pick the collective brains. Have a problem with the air conditioning on a GTI, it was checked and recharged last March and seemed Ok through the summer but now fails to produce cold air. Compressor engages and the fan kick in as it should. I've had a garage take a look and they're saying there's evidence of a small refrigerant leak in the hose which contains the pressure switch. Cost all in, in excess of £500. 
The hose is on back order from Germany, so do I bite the bullet and spend the money or try and source a second hand hose? your collective thoughts please .... and NO keeping the windows open in the long term isn't an option before anyone says 😀

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Hose or pipe? Pipe could be tig welded. It'd be fairly easy to make a hose if you go to someone like Pirtek. But I guess it needs to be ac hose, not hydraulic. I'm sure most industrial refrigeration specialists would be able to knock one up while you wait. Something like a tenner...

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3 minutes ago, mk2 said:

Hose or pipe? Pipe could be tig welded. It'd be fairly easy to make a hose if you go to someone like Pirtek. But I guess it needs to be ac hose, not hydraulic. I'm sure most industrial refrigeration specialists would be able to knock one up while you wait. Something like a tenner...

That's a thought, haven't seen the pipe myself as its under wheelarch, they said pipe not hose and I wondered whether using second hand hoses for A/C would be wise or false economy.

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I have some.

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6 hours ago, Rich said:

I have some.

That sounds hopeful Rich, from th description they gave I'm thinking its pipe 7 on the diagram.

Capture.PNG

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I think you should find a second hand hose. 

Or to fix the existing where the leakage is.

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It's still in the car.

Gimme a week or so as it's not easy to get out.

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44 minutes ago, Rich said:

It's still in the car.

Gimme a week or so as it's not easy to get out.

Cheers Rich, I'll have a look this weekend to confirm exactly where the leak is 🙂

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I don't know the feasibility of fitting it with an engine in mind.

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8 minutes ago, Rich said:

I don't know the feasibility of fitting it with an engine in mind.

Ahhhh ..... might have to live with the windows open in the summer 🤣🤣 I'll have a good look in the next few days and check the routing.

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Under the engine mount bracket.

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I wouldn't mind betting that the pressure switch has failed and is giving a false high reading. If you just had a leak (and low pressure), the fan wouldn't run. The pump always runs (even when A/C is off) unless the safety "clutch" has failed, which happens when the pump has seized.

RAB

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Service union under the brake servo.

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If pipe 5 in the drawing gets hot when the pump is running (ac selected), it means you're compressing gas, so you 'should' get some cold. @RAB is right about the switch though. There's a high low switch which cuts off the compressor (to avoid damage). Too high- off. Too low- off. Somewhere inbetween - on. The clutch should engage and disengage as you select AC. You can see the flat plate bit, furthest from the pump, in the middle of the pulley. When off, it shouldn't turn. When on, the electromagnet pulls on it engaging the plate clutch. Very simple system. Usually the bearing wears out before the compressor packs up. New compressor seals are about £3- little ceramic graphite things, a bit like a ceramic tap valve. My bet is that the evaporator (bit inside the car is clogged with gunge= low air flow), or like you say lowish gas. The fan should run when ac is on.

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Thanks for the help guys, I've spoken with the guy who checked the air con and he's saying there's evidence of dye in two places .... above and below the pressure switch, I ran out of time to jack the car and check myself but am wondering if this is a leak from a holed pipe or as @RAB says a failing/failed switch spraying a mist onto the pipe. Engaging the A/C gets a noticeable change in engine note followed shortly after by the fan kicking in. When the system was recharged last year it worked well and over the year became less effective (though used less). Thanks for tip @mk2 I'll check pipe 5 for heat. 
Being of a certain age I tend to not to walk under ladders etc but note that the pressure switch seal is numbered 13 ...... I wonder??🤔

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There's no clutch on the pump. When the A/C is off, the pump still runs but at a minimum level, determined by the swash plate.

RAB

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Ah, ok, it's one of those compressors... In that case, check the power feed to the control valve, going into the back of the compressor. It's the thing that sets how much volume the pump displaces (how much it compresses per rev).

Disregard my previous post, as that applies to the other type of compressor. @RAB is right as usual. :)

 

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So the GTI has a variable displacement compressor? I thought they were quite a recent thing.

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6 hours ago, dirk1978 said:

So the GTI has a variable displacement compressor? I thought they were quite a recent thing.

Me too. @RAB has played with way too much mechanical stuff obviously... :)

Merc only started using them around 2002, so obviously vdub thought that the lupo gti was a worthy candidate. Polos and golfs of that era certainly have the old clutch system. I don't like them. It doesn't rest well with me, that the complete internals are spinning away at the same RPMs as the engine, and not doing any work. Nothing wrong with the old clutch design that's been around for decades. Clunky, not elegant, but works very well. My fav are the vane compressors. Hardly any moving parts and ever so reliable. Smaller too.

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7 minutes ago, mk2 said:

Me too. @RAB has played with way too much mechanical stuff obviously... :)

Merc only started using them around 2002, so obviously vdub thought that the lupo gti was a worthy candidate. Polos and golfs of that era certainly have the old clutch system. I don't like them. It doesn't rest well with me, that the complete internals are spinning away at the same RPMs as the engine, and not doing any work. Nothing wrong with the old clutch design that's been around for decades. Clunky, not elegant, but works very well. My fav are the vane compressors. Hardly any moving parts and ever so reliable. Smaller too.

My 2007 early mk2 Octavia VRS had them and the aircon guy who replaced the whole system when it failed described how they worked to me because they were fairly new.

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I'm wrong! I was making the assumption that Lupo A/C would be the same as Audi A2's; not unreasonable? The Lupo clutch is, according to Etka, electro-mechanical whereas the A2 has no clutch. The Up is the same as the Lupo. Never make assumptions!

RAB

 

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10 hours ago, RAB said:

I'm wrong! I was making the assumption that Lupo A/C would be the same as Audi A2's; not unreasonable? The Lupo clutch is, according to Etka, electro-mechanical whereas the A2 has no clutch. The Up is the same as the Lupo. Never make assumptions!

RAB

 

Now that @RAB has achieved 'wrong' status, i think we need to ask @MattyB to upgrade him to 'premium' membership. What d'ya think peoples?

Edited by mk2

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No

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