Greetings.
Last year I had to replace the cam seals due to a MASSIVE leak the were allowing, due to a prior shop installing no-name seals (during a timing belt/water pump scheduled replacement) that failed after only 20k miles.
That job was done successfully, by me, but now after the AC system was recharged (pulled down so I could remove the lines to do the aformentioned seals more easily) the AC system won't turn on.
I own an Autel MaxiSys 906Pro, and I can go in and manually engage the compressor (I don't run it for long, for fear of causing an overpressure condition.)
I've tested the fans, compressor, refrigerant pressure (using gauges), control states, command requests, anything I can think of and can test/control with the tool.
When I do turn the compressor on, the high pressure line gets cold, the cabin gets chilled air, but I can't activate the system from the controls.



You can see that, the Pressure Voltage is stuck at 5v, and the Pressure value is stuck at 580 psi, but I can't for the life of me find that sensor on the car, or in the OEM service & repair manual, which I have a copy For the snapshot above, the tool is commanding the compressor on, the blower is on high, and the AC button is pressed (light is on.) Again I've tested comms on the car and the CGM is seeing the button being pressed, but it won't command the compressor to turn on, due to I suspect the pressure reading being sky high. The only item of question on this car, is the high pressure *switch* on the compressor itself looks a little suspect, in that it has a chip out of the green part of the plastic body of it. I thought that was only a switch though, since it's a 2-wire connection. Every other chrylser I own has a 3-wire sensor connected to the high side line coming out of the compressor, except for this PT cruiser.

If anyone has any thoughts on this I'd appreciate it.

 

5v on that circuit means its unpluged and the high side pressure is a a defaut number because if it was really 500 psi the manual popoff valve would be spewing out the freon from the compressor. so you likey have a high side switch issue or a wire issue to that switch .

 

thanks for the reply. so translation from voltage to pressure, according to the tool, isn't really happening I guess? I'm looking at the diagram

and it's showing it's just a pure switch. so I should just ignore the pressure reading and focus on the voltage reading I guess. If so, that means it could be either switch that's failed, and I've been chasing a rogue thinking there's an actual pressure sensor I've missed someplace.

 

the high side switch along with the low side switch is just to act as a safety item. Low pressure it turns off the clutch high pressure it turns off the clutch. .
Go to the high side sensor make sure when unplugged it has 5volts and the ground present . The next easy way after that is plug the sensor back in go to the low side disconnect it measure the voltage again if you have less then 5 volts there then the sensor is messed up. because it should just pass the voltage right through if the actual high side pressure is below the 580 psi. Can do this to put a jumper wire between the circuit on the high side connector at the compressor then look at your scanner turn on the ac see what it looks like.
If the ac works well then you have you answer

 

So just as a follow up: I've found the problem. the ground on the low pressure switch, isn't grounded. somewhere between the connector and G105 there's apparently a break in the wire.

 

that will go it all the voltage is staying in the circuit instead of going to ground.

 

yep. luckily the weather's been mild still, and mom doesn't use the A/C all that much; she was cold in Hawai'i!
I'll get the car back, spend some time trying to find the break, but if I fail i'll just pigtail the ground wire and terminate it on the passenger strut tower ground, and call it a day.
I must have done something when I was doing the cam seals, all that engine up and down or something.