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Discussion Starter #1
My wife’s a/c went out back in the winter. Now we’re racing to get it going. Awhile back I was reading about the control solenoid and replaced it with a RKX control valve. It seemed like the compressor was shot as I was getting no suction as both high/ low are at equal pressures. Combine that with everything I’ve read about the sanden compressor it came with is garbage. I decided to replace the compressor. Changed the compressor with a Murray from O’Reily’s And the expansion valve. Vacuumed it down and began to put Freon in. As I put Freon in on the low side (before starting it) it was starting to go up on the high side which would indicate no restrictions. Started the car fan high a/c set on max And then there’s no suction on the low side like the compressor is not working. So thinking I got a defective compressor or maybe one with a bad clutch, I go get another one installed it and same thing, no suction. So I said all of that to ask this does the control solenoid turn on and off the compressor? I start the car hot day at idle and I am adding Freon what is stopping it and how can I diagnose it. Pressure switch? I do have vagcom rosstech Thanks in advance
 

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When you say “no suction” do mean low side doesn’t drop from, say 80 psi, down to 30 when the compressor starts?

Yes, could be the pressure switch, but you can see it’s pressure reading in Vagcom.

Also verify you haven’t swapped teh solenoid connector with the connector to the aux coolant pump, which is right next to it on the harness (this has been done before).
 

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Are you certain the compressor is running? You should hear the clutch engage and notice the slight load on the engine as well when you hit the AC sw. While the outer portion of the compressor pulley rotates with the belt, if the compressor clutch is not engaged via the 12vdc source thru the 384 relay, the compressor is not running and suction pressure will not drop.
 

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Discussion Starter #4
UPDATE - So I know that the compressor clutch is always engaged with a shear pin. If the compressor were to fail it would shear off and not tear up the belt. The solenoid on the bottom controls whether the compressor is working or not. In my case we changed the compressor, expansion valve, added the oil and vacuumed. When we initially put the Freon in we opened both gauges and as Freon went in on the low side you could see the high side starting to move so no blockage. ran it but couldn't get the compressor to work or pull downlow side. Put power to the compressor and it immediately gets cold. so we changed the pressure switch and I have vagcom and the HVAC module DTC was
00819 - High Pressure Sensor (G65)
009 - Open or Short to Ground
After clearing the dtc we tried again nothing thought it was maybe a bad pressure switch (the new one) so I got another one nothing. So I'm thinking its the ground from the ECM that turns hot to energize the solenoid or does the pressure switch have to be OEM? As
for another plug by the pressure switch theirs only 2 and niether would work. Now to the fuses and relays. ` Under the steering wheel relays Does it look like something is missing? Of the ones there I switched the 2 53's, the 449's and the 2 460's. don't see a 384. their was electrical work done last winter when it quit that's why I ask could it have been removed and not put back?
image1 (1).jpeg

Refered to owners manual and checked fuses in cabin left side and right as well as under the hood all good. So that's where I stand at this point. If I clear the code and go back to the page before, then click on the codes its right back. don't know how to do very much with vagcom. But I can try something else using it if somebody has any ideas. Thanks in advance for any help and forgive me for rambling
 

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In Vagcom, not sure where, but I think under the engine control module you can see compressor load and amps (at least on my ‘13 CC). See if this changes when you hit the ac button on the climate control unit.
 

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Discussion Starter #6
Thank you for the input I will sure give it a try. I watched a video where the mechanic had a scope screen up and it had a line going across with little blips and he took a test light hooked to battery ground and was tapping on one of the wires off the pressure switch which made those little blips turn into spikes and as long as he was tapping on the wire the car was cold. After that test they changed the pressure switch. I know their is a scope on vagcom but don’t know how to get it to show the AC circuit
 

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Discussion Starter #7
Ok the compressor works with 12 volts to the brown wire but the pressure switch is not sending the signal. I'm on the second NEW pressure switch. I need a wiring diagram of the wires on the pressure switch going to and from the switch if anybody can steer me in the right direction
 
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