RS2 Aircon problems

[trevithick]

The problem being it doesn't work.
The light comes on and the fan runs but the compressor isn't engaging. i've put 12 v to the comp. and it engages fine.
I've noticed that relay 6 is missing, I swapped the horn relay into the position and it engages but still no compressor.
Has anyone got an idea of what is wrong and does anyone have a wiring diagram for this system, that would help (I'm an electrical engineer so I stand a fighting chance).
HELP its' a black car and the summer's comming and we're getting a bit hot.
Cheers
T

[RAOUL]

I take you have had it gassed? I might be wrong but if you've no gas in i dont think it will engage the clutch. I lost my gas due to a hole near the fitting in front of the brake reservoir. Apparently its a common fault? Anyhow bought a pipe of VagParts that doesnt fit so i've had the pipe welded up but not gassed it yet. Hope this helps without insulting your intelligence.

[trevithick]

The previous owner had it regassed but I was wondering about a leak somewhere and I wanted to get other possible causes out of the way first.
I'm a bit confused about the missing relay as Dickyc said it was working fine after the last gas?
Cheers for the reply I'm going to check that fitting (i've got a set of aircon gauges and pipes so I may be able to check for pressure if they fit).
Thanks
T

[s2driveruk]

yep if no or low gas then it won't work the compressor even if the clutch is clicking etc. BTDT last summer on my coupe. Soon as there is enough gas in the system it will work. if you have removed the recharge port and depressed the pin to make some escape, more than likely just compressed air...

hope that helps
David

[trevithick]

Cheers any idea what the gas is, R134a ? I've got some of that, or the Cornishmoocher could top it up.
T

[RAOUL]

My coupe is R134a, sticker is on the bonnet. Just nipped out and took a couple of pics. The pre-formed ally pipe that disappears into the wing has a heat proof wrap/ sleeve, i think its said sleeve that rubs through the pipe to be honest. When i tried to split it from the drier (behind front bumper) i couldnt hence having the original welded up. Hop this helps brother.

[merlin's S4]

Check you MFTS. It's the big temp sensor in the water manifold. If this is faulty it can stop the compressor working. The easiest way to test it is to unplug it, start the engine and then try the aircon. If it works then you either have a faulty sensor or very often the connector to the MFTS has corroded.

[s2driveruk]

RS2 will be gassed with R134a yes, earlier cars (like mine) were using R12 but that was discontinued at the end of 1992 by law. Even if you don't know for sure the port will be specific to the refrridgerant used and any competent aircon specialist will know for sure.

[trevithick]

I'm going to put the suggestions into practice today.
Cheers all
T

[johne]

The wiring diagrams are on S2central.net

The low pressure switch controls whether the compressor kicks in or not and there needs to be 45 psi of pressure in the system to hold that pressure switch closed. By all accounts you're most likely out of gas.

Your car is filled with R134a gas which is the only one you can use these days. However earlier cars that used R12 can be easily and cheaply converted to R134 so there's no need for early guys to be hot!

There are posts in the heating and aircon section on here with more detail.

John

[trevithick]

Its' me gas.
I took the dust cover off the HP port and opened the port and it sounded like Elton John farting, so all me gas has gone time to find the leaky.
Does anyone know what size the connection is on the pump, I've got a few R134a connections but not that one?
Cheers
T
ps someone is kindly sending me the diagrams the manuals I bought off fleabay don't work.

[johne]

The connector on the pump will fit the yellow coloured hose in some A/C gauge kits but I recommend recharging through the high pressure port on the radiator - but with the engine NOT running!

Otherwise you may have a low pressure port up behind the ECU in the passenger footwell but it's a pig to get to.

John

[trevithick]

Any idea what the port on the back of the pump does?
T

[johne]

No, other than it's a port into the system and on mine it is a screw thread rather than a quick connect like the other ports. I don't know if it's on the low pressure or high pressure side but I did charge and oil my system through it the first time to ensure there was oil in the compressor before it first started. Since then I've used the high pressure port on the radiator to recharge - but never with the engine running.

A brand new compressor should be capped and filled with dry nitrogen so that port would let the manufactuer do that. The other part on my compressor that looks a bit like a port is the emergency high pressure relief valve to protect the system/compressor if all else fails.

John

[trevithick]

I've chucked a load of gas in the HP side (using my "home made" system), and I have cold air so things are looking up but I need to find the leak now (it must have one).
It must be a fair leak as it was only recharged earlier this year but it was done by Audi so they possibly didn't give it a full charge (obviously not saying that they may have charged for something they didn't do, that would be wrong obviously)
Anyway back to it I ned to earn some dosh as this motor keeps swallowing it.
Cheers
T