A4 B6 Weird A/C Issue

[rowdy-999]

My A/C had never worked.
I replaced a seized denso conpressor with an brand new identical hella unit. Pro filled with correct amount etc..New dryer and orifice tube.
The a/c worked brill for about 2 weeks, then became intermittent as in the a/c rad fan stops and no chilled air. The econ light remains off as it should..
When it works its nice and cold. Could be on for 1 hour or only 2 mins before switching off. Then may come back on again.
No fault codes.
I tried a new climatronic and g65. No change.
Ive had the pressures checked and all is normal. No leaks.

Ive checked the wiring to the compressor and g65.
All the readings seem normal apart from the high pressure signal (g65 ) which is a constant 0.0%
Sometimes if i boot it and raise the rpm the compressor kicks in, but not always.

My theories are....duff new compressor, debris in the system, wrong g65 sensor fitted ...its 3R0959126 currently.

Any ideas?

[Rob69]

you might still have a leak, as pressure alone will not tell you how much refrigerant is in the system, the liquid level could have dropped to virtually nil as gas leaks and liquid boils off. have you gone round all joints with leak detector solution like snoop, only way to be sure would be to evacuate and see how much comes out if the air con machine can do that, then recharge with correct mass. when it does work do you hear a gurgling noise under the dash?, where the evaporator would be. I've had cars low on charge that gurgle at the evaporator, and AC perform poorly. I think this is due to low liquid level from the condenser and gas coming up to the evaporator / expansion orifice. you could get a cheap gauge set off ebay if you want to check pressures yourself.
here's some info I've found useful in the past on rosstech wiki
Tis’ the HVAC Season (https://forums.ross-tech.com/showthread.php?633-Tis%92-the-HVAC-Season)

[rowdy-999]

There's dye in the system and i can see no obvious leaks.
No gurgling. When it works it blows very cold.
The a/c mechanic used an electronic stethoscope type device and listened to all the joints for a leak.

[Rob69]

If it's the age and type of compressor on a B6 I'm thinking of are you sure the clutch is engaging properly, I've had to play around with the shimming on a Denso compressor clutch with the rubber drive element on a B5.5 passat I used to have, to get it to disengage, does your clutch get very hot, ie could it be slipping when engaged. seems strange how when you rev it, it might work or it might run for a few minutes or an hour

[rowdy-999]

It's not the type of pulley where the centre of the pulley only turns when it's engaged. The whole thing turns all the time.... Not sure if it has a clutch ot not.
Ive not checked it for heat.
Thanks for your input so far..