Aircon pump

[big_tedman]

Aircon has been substandard since i got the car - 99/00 mk4 gti
so we went to recharge it but the pump doesnt seem to be running. When the aircon is
turned on the pump engages, but pressure within the system doesnt change.
I have checked both the high and low points.
Before i go buy another compressor, what else could i check?
not sure if VW have something uber special with the system?

[JustCruisn]

There are a few things that go wrong.
1. The thermo fans don't jump to high speed when they need to. Sometimes a broken resistor in the fan.
2. The control unit is stuffed. It is mounted below the battery and has 2 huge connectors on it.
3. The field coil is gone.

The brains is the control box. It takes signals from pressure sensor (drivers side firewall), thermo fan setting, throttle position (from Engine ECU), ambient outside temp (under bumper left side), cabin on off switch. From all this it decides when to turn on the fans and compressor.

You say it engages. Have you watched the pulley actually spin in the middle to confirm this ?
The engine will pick up revs when ever the compressor should be on, so that is not a good test.

[Jmac]

Yeah mate you pretty much summed it up, if you fit gauges to your car they will just stay put with the compressor running, im sure by the sounds the compressor is defunkt. They are a variable displacement compressor and im sure itll be stuck on its stroke and itll be all scored inside, fairly common, if you look for a replacement you must get the exact one as the duty cycle is different between 4 cyls and 6cyls.
Have someone fit a set of gauges as they never lie if they are stuck and compressor runs itll be the compressor

Cheers
Jmac

[JustCruisn]

This is probably be exactly what you need, check your part number.

http://www.vwwatercooled.com/forums/f24/air-con-compressor-mk4-78225.html

Your timing could not be better. VW charge $1200 for a new compressor or $747 just for the field coil.

[Jmac]

This is probably be exactly what you need, check your part number.

http://www.vwwatercooled.com/forums/f24/air-con-compressor-mk4-78225.html

Your timing could not be better. VW charge $1200 for a new compressor or $747 just for the field coil.

Yep x 2 here, just check all your numbers match, check the pressures are good but stuck with it running and then get yourself a bargain
Cheers
Jmac

[big_tedman]

Thanks guys. Compressor engages and starts spinning. So I'd say the compressor. Ill check my numbers in the morn and check that one out. Might work well and good timing

[MK4Golf]

Cheaper option?

http://www.vwwatercooled.com/forums/f24/air-con-compressor-mk4-78225.html

[big_tedman]

Just to make sure vw haven't done something strange. If the compressor clutch engages, I can see it start spinning, can the compressor work without any change in pressure? Gauges sat on about 40psi and didn't move on both high and low side. Normally that means compressor is dead, just want to be sure

[gringo_54_oval]

Im going through the exact same issue. No pressue on the ac gas. Mechanic said compressor is dead. Great just what i need before xmas!

[Manaz]

If you get me the part number, I can see what sort of price I can arrange from ECSTuning...

[Jmac]

Yes even with it spinning and clutch in if the pressures just sit the compressor is stuck inside at a certain part of its stroke and im sure itll be all scored inside. It a variable displacement compressor. Itll most likely be a Sanden SDV16 . But the serial must be the same as there is a couple of these Very similar so all your numbers must be checked. Cant stress that one enough
Cheers
Jmac