Question on Charging A/c

[bobflood]

Just figured it out. No I don't have that function. All manual controls.

OK - then you need to do some electrical "sectionalization" of the circuit. I apologize in advance if the following instructions are too basic, but I don't know what your comfort level is with electrical troubleshooting.

The path is pretty straigthforward:
- You have battery (12V) coming into the HVAC switch on the control panel on a white/purple wire whenever the ignition switch is in "On" position. When the HVAC switch is set to Norm, Max or Defrost it places 12V onto a purple wire to the "cycling switch" on the low pressure side. This switch cycles the compressor on/off as necessary based on the low side pressure. (Temperature control is provided by moving the blend door, not cycling the compressor).
- When the cycling switch closes, it puts 12V on a red/yellow wire that connects to the "high side pressure switch" - this switch is normally closed, it opens if the pressure gets too high and is a safety measure.
- The high pressure switch puts 12V on a dark green/orange wire that goes two places - the Power Train Module (PCM) and the Wide Open Throttle (WOT) relay. The WOT relay is normally closed, it opens when the PCM detects WOT and shuts off the compressor so the compressor is not pulling engine power away from the drivetrain.
- The WOT relay puts 12V on a black/yellow wire that runs to the compressor clutch; the other side of the compressor clutch is grounded thru a black wire.

You said that putting 12v from the battery directly to the compressor clutch operated it normally and that you got cooling - that means that the compressor and clutch are fine.

Get yourself a 12V test light, ground one side at the battery, turn the igniton switch to "On" (engine does not have to be running) and start testing the circuit from the input to the compressor clutch back to the control panel thru each of the devices listed above. Take them in reverse order, starting with the input to the compressor clutch. Unplug each device in sequence and test the input side of the connector - when the test light lights up, you know that everything back thru to the battery from that point is OK. Good luck.

 

[Lefty2053]

OK - then you need to do some electrical "sectionalization" of the circuit. I apologize in advance if the following instructions are too basic, but I don't know what your comfort level is with electrical troubleshooting.

The path is pretty straigthforward:
- You have battery (12V) coming into the HVAC switch on the control panel on a white/purple wire whenever the ignition switch is in "On" position. When the HVAC switch is set to Norm, Max or Defrost it places 12V onto a purple wire to the "cycling switch" on the low pressure side. This switch cycles the compressor on/off as necessary based on the low side pressure. (Temperature control is provided by moving the blend door, not cycling the compressor).
- When the cycling switch closes, it puts 12V on a red/yellow wire that connects to the "high side pressure switch" - this switch is normally closed, it opens if the pressure gets too high and is a safety measure.
- The high pressure switch puts 12V on a dark green/orange wire that goes two places - the Power Train Module (PCM) and the Wide Open Throttle (WOT) relay. The WOT relay is normally closed, it opens when the PCM detects WOT and shuts off the compressor so the compressor is not pulling engine power away from the drivetrain.
- The WOT relay puts 12V on a black/yellow wire that runs to the compressor clutch; the other side of the compressor clutch is grounded thru a black wire.

You said that putting 12v from the battery directly to the compressor clutch operated it normally and that you got cooling - that means that the compressor and clutch are fine.

Get yourself a 12V test light, ground one side at the battery, turn the igniton switch to "On" (engine does not have to be running) and start testing the circuit from the input to the compressor clutch back to the control panel thru each of the devices listed above. Take them in reverse order, starting with the input to the compressor clutch. Unplug each device in sequence and test the input side of the connector - when the test light lights up, you know that everything back thru to the battery from that point is OK. Good luck.

I will buy a test light today and give it a try. Thanks for all the help.
If Say I test the Wires going to the Low side and the light doesn't come on then what? Is that plug bad or the wiring going to that plug?

 

[Maniak]

It will depends on which side you see power on, if either.

If you get no power on either side of the low pressure switch then the signal from the a/c switch isn't making it to the low pressure switch.

If you check the low pressure switch and you find 12v on the input but not the output then either you don't have enough pressure or the pressure switch is bad. If either of those is the case when you jump over that switch the compressor would turn on.

IIRC you tried to jump over the low pressure switch and it didn't work which tells me the issue is before that switch or between the switch and the compressor (which is why you want to check the wires at the pressure switch with the test light)


~Mark

 

[bobflood]

I will buy a test light today and give it a try. Thanks for all the help.
If Say I test the Wires going to the Low side and the light doesn't come on then what? Is that plug bad or the wiring going to that plug?

The problem could be anywhere between the input side of the low pressure plug and the battery if no 12V at the input side of that connector. However, wires don't usually go bad -if you have no 12V at that plug, I would suspect the control panel switch or the associated plug being bad before a wire. You just have to keep moving back toward the battery until the light goes on. BTW, power comes from fuse #18 in the fuse box inside the driver's door.

Personally - I would first suspect that the WOT relay is the problem. Either the relay itself could be defective, or for some reason the PCM is operating it all of the time instead of just at WOT. If you have 12V at the WOT socket for the dark green/orange wire, I would replace the WOT relay with a jumper between the socket holes for the black/yellow and dark green/orange wires. This will duplicate the normally closed position of the relay. If that works, it would indicate that the WOT relay is being held open all of the time instead of just at WOT. Good luck.

 

[Lefty2053]

Thanks for all the help I will try and do all this by the weekend.

 

[Lefty2053]

Update

Ok took it in today and had the tech figure it out. He put it on his Snapon Device and it said the wot relay was turned off as it should be. But when testing the circuit itself it showed that it was turned on which would stop the A/c from coming on. He said I had 2 choices.
1. Bring it back in another day and he would track down the short circuit.
2. He would put in a jumper wire and it wouldn't hurt a thing except I wouldn't have the A/c shut down when WOT for passing.

I told him the wire sounded good to me.

$60 and the A/c runs you out of there.
I will open up the Fuse box when the temps get back to low 80's and find the wire that is shorted out. Almost 100 degrees today here.
My Jetta had too much R134 in it and he charged me $37.50 to fix it. I can live with $97.50 to get both A/C's working in these temps.

Thanks for all your help here.