AC compressor not tripping?! MKIII AAZ.

[Torchd]

I got the AC system recharged and it working well now but the compressor doesn't trip and the guy working on the system said that it should. So should it? People here are not experienced when it comes to VW's since they are rare cars.

Where is the thermostat which is responsoble for tripping the compressor and how can the fault be rectified? If any one has wiring schematics for this thermostat then please share. Please let me know if this is not the place where I can get relevan replies since I presume most mkIII's in Canada wouldn't have an air con.

[the caveman]

If you are sure the exact amount of r 134 is in the system, the next thing I would check is the hi/low pressure switch. It's mounted on the bottom of the dryer. Remove the connector, and short out # 1 and 2 pins on the connector. This will make the module think the pressure is where it sould be. If this causes the compressor to come on and start cooling, it's the switch. If not you will have to check the intake temp sensor , ambient sensor etc. All of that part of the circiut is in series, so if one part doesn't work, nothing will

[pointynoggin]

My mk2 ac clutch is daisy chained with three switches.  low pressure 'NO' ( no gas present) high pressure 'NC' (system is compressed enough for cooling) and a thermo switch 'NO' inside the car.

I have never laid eyes on the thermostat and hope I will never have to.  The other switches are on the same line between the pump and the compressor.  with the car off unplug and check continuity across the switches.  I think that there is a thermo switch as well on mine on a coolant line that the circuit goes thru as well.  Might be to keep the ac of till warm enough to maintain idle speed.

follow the clutch wires and check the switches.

If this looks familiar and you still have trouble I can trace is out better for you.

[Baron VonZeppelin]

Torchd ,
Do you mean the AC is working and cooling the car good -
but the compressor never cycles off periodically ?

[Torchd]

Torchd ,
Do you mean the AC is working and cooling the car good -
but the compressor never cycles off periodically ?

Yes thats exactly what I mean. AC is working and cooling fine but the compressor doesn't cycle. Is this how it is suppose to be or is there anything wrong?

[dieselweasel]

I'm not an a/c expert, but I believe that in the type of system on your car (TXV), the compressor should only turn off if the system pressure gets too high or too low.  Refrigerant flow to the evaporator is controlled by the expansion valve.  Many other manufactures use CCOT systems in which the compressor IS supposed to cycle, to conrol refrigerant flow.  In other words I believe your system is working as intended.

[Torchd]

Right.

Can someone else please confirm this?

I Don't wanna break anything else assuming there is something wrong with it since parts are a bi*ch to source here.

Thanks!

[Torchd]

I'm not an a/c expert, but I believe that in the type of system on your car (TXV), the compressor should only turn off if the system pressure gets too high or too low.  Refrigerant flow to the evaporator is controlled by the expansion valve.  Many other manufactures use CCOT systems in which the compressor IS supposed to cycle, to conrol refrigerant flow.  In other words I believe your system is working as intended.

Thanks... Just wanted to ask which system does MKII have, TXV or CCOT? I have a MKII 89, MF and the compressor in cycle, the components in MKII and MKIII look quite similar to an untrained eye like mine.

[dieselweasel]

Thanks... Just wanted to ask which system does MKII have, TXV or CCOT? I have a MKII 89, MF and the compressor in cycle, the components in MKII and MKIII look quite similar to an untrained eye like mine.

[/quote]

Couldn't tell you.  A google search came up with this forum that you may want to post your questions in: http://www.autoacforum.com/.  Let us know what you learn.