Air Conditioning Issue

[Factorytrooper]

Well for starters. Car is 2000 A4 quattro and I have had a problem with my ac for the past few months. It works sometimes like in the morning or at night but during really hot days the compressor keep shutting off. The fan near engine intantly turns on when I turn on the AC. My outside temp reads correct.

When it does work its really cold so i'm guess the compresor is still ok...

What could be the issue?

[MattzWarsteiner]

High pressure switch may be kicking in. You may have a bad switch, overcharged system or a restriction. Have a look at your condenser to see if it has anything blocking the airflow. This is in front of the radiator.

[Factorytrooper]

LOL Yea I know where the condenser is. Clue me in on the location of the pressure switch, that would be cool. I will pressure test the system and see if its over/under charged.

I will update when tested.

Thanks

[MattzWarsteiner]

Switch is next to the passenger headlamp assy. Have you any codes from the CC module? You can troubleshoot alot of this using just the CC buttons in diagnostic mode.

Control head can also report trouble codes using this DIY if you don't have VAG COM software. Read out function 22, 23 and 29 in that DIY would be useful information since it relates to the HP switch.

Not trying to get ahead of the search, but the ECU and on Tip cars, the TCU can command the compressor off too. The channel 52 in that same DIY will tell you why the comp is off if its a command thing.

LOL Yea I know where the condenser is.

Hehe, well you never know.....

[Factorytrooper]

Wow, who knew the CC diagnostic could do so much.

Here is what I GOT:

Under system Malfunction two error codes came up

code1
13.7 - Footwell/Defroster Flap Sporadic block
22.3 - A/C Refrigerant High Presure Switch, Sporadic open

code22 - 1
code23 - 0
code29 - 57
code52 - 0

I'm not to sure about the 1,0 and 57...

Any help on what sporadic open high pressure is

Thanks,
Jesse

[MattzWarsteiner]

22.3 - A/C Refrigerant High Presure Switch, Sporadic open

Hey, Jesse, that is the HP switch code. You can troubleshoot this with a couple of pieces of wire at the HP switch on the condenser.

With the switch harness connector disconnected, looking into the harness side with the retaining clip boss on top and terminal blades oriented horizontally:

Red/Green & Brown wires are for the cooling fan. They should be the top pair. This makes the fan run when pressure builds up in the condenser. You can confirm by shorting these two with the engine on. The fan should run.

At the bottom are possibly brown/blue & brown/white wires. This is the high pressure signal to the climate control module. Leave connector open and try AC. If compressor is off, short these two wires together. You may have to hit the snowflake on the CC panel to toggle it back on.

Don't recommend this arrangement for long ..... if there is an actual high pressure buildup, you could damage the compressor or cause the pressure valve to release R-134. The highest system pressures will be on hot days and also when not moving or if there is a blockage.

[Factorytrooper]

Thanks for the explanation. It does bypass it but there is a pressure buildup. I believe if my meter was right there is over 3lbs in the system. What is the proper pressure setting and/or the amount of r134 in the system. So The guy I brought it to could flush the system and input the right amounts. Also should I change the dryer if this is done?

Thanks,

[MattzWarsteiner]

Glad to help out FT!
The HP cutout switch should open at around 400psi. The coolant fan should be running @ 200-250psi and above on the high side. Depending on the outside air temp, the charge pressure ..AC off.. should be around 70-90psi.

If you do get the flush & recharge, I would go for the dryer yes. Its considered good practice in auto air service. There is an orifice tube at the connection to the evaporator that should be replaced. Its cheap and sometimes clogs when the accumulator blows its guts into the system. Yours may be perfectly fine.