Articus

Hi all,

I have a 2001 1.8T Quattro whose air conditioning stopped working in the spring. There are no VAGCOM codes for compressor shutoff conditions. The relay clicks, the compressor turns on, and the condenser fan spins when it is supposed to.

I got an A/C pressure gauge kit and tooks some readings.

Off (compressor had not been used all day)
High Side: ~100 psi
Low Side: ~100psi

A/C On (Compressor On)
High Side: ~126psi
Low Side: ~26psi

This looks good to me. When off the pressure equalizes, and when on the pressure on the high side goes up, low side goes down.

Possible Causes?

1) Blend door: If it were stuck, hot air is mixing with the cool air and producing warm air so I pulled the glove box and watched the red blend door actuator moving through it's range as I lowered and raised the temp from the climatronic. All good with the blend door. No problems here.

2) Orifice tube clogged? (But then wouldn't the high pressure side go too high and trip a compressor shutoff code?

I cannot figure out what is wrong with the system. Could it be low on refrigerant even though the pressures look normal? I read that r134a vapor pressure is constant at a temp regardless of the level of liquid freon in the system so even with a low amount of Freon, you would still see pressure, but the condensor is not full and hence no cooling. Any ideas?

Articus

and please oh PLEASe don't let this be evaporator failure....If that evap needs replacing, Im going to have to do with A/C until I can get a second car and have this one for a week to get the dash out...

David.Norton

Not sure what is going on, but start by splitting your problem, if the line coming back from the evaporator is cold then your problem is in the air control in the dash, if not then you have an issue in the freon circuit.

Articus

Alright I just checked the tubes where the shcrader valve connections are. The high pressure line was the very cold one and had a lot of condensation on it. The low pressure line just ambient temperature. So this is pointing to some kind of restriction in the high pressure line causing pressure drop near the valve.

Does anyone have an overall a/c system diagram? I think it might be the A/C drier but I want to see a diagram to pin point anything else that could cause blockage.

Articus

Alright here is some more details as I look into this. Labeled the audi catalog diagram:




Determined the correct flow direction from this the B5 Passat self study guide (a/c systems are pretty universal in operation though). Grabbed this for no other reason that it's a really nice diagram.

Articus

And with that said, If the tubing is cold on what seems like the outlet of the evaporator to the drier, that would point to a blockage in the evaporator itself right?

Also why aren't both tubes cold (if anything at all)? I realize in a normal working system the low pressure line should be the cold one. The high pressure refrigerant first crosses the orifice tube so there should be pressure drop here right and that tube should get cold. Why would that tube not be cold but the exit of the evaporator would be very cold? Almost like the orifice tube is burst open or leaking and the high pressure is in the evaporator itself. That can't be good...

Prospeeder

I would pull out the orifice tube and look, its fine mesh screens can plug full of junk. That very low suction side is the compressor pulling against a blockage. Discharge the system and its under the cabin filter under the hood, the 8mm allen bolt holds the 2 pipes in, and if you look up further on the smaller line, there is another fitting, remove that, remove the little piece of pipe, Inside is the orifice tube. Make sure you put a new one in the same way. Normal pressures are like 40 low and 250 high on a 80-90 degree day. A high side of 126 is not removing heat at all. Probably the blocked orifice tube. They are the same as GM cars, so your local parts store like Napa or what ever should keep one, they are like 4$ lol.