Climatronic not working, no TDCs

TDIaholic

Member
I'm a bit stumped, as the AC in my wife's car is refusing to blow cold air. Can you guys help?

Current situation:
- Compressor & dryer changed in 2015 acc. to the service book. There is a minimal amount of axial play on the compressor pulley, and the pulley center and the pulley itself rotate together, so I gather the compressor should be good. The electrical connector on the back is secure, but the bit it attaches to feels lose on the compressor body. Is this normal?
- No fault codes. The only code I had was from th G263 sensor, which I changed and the code cleared with VCDS.
- The system shows an absolute pressure of 6,5-7,5 bar when looking at measuring blocks on VCDS. However, hooked up to an external meter there is no actual pressure in the system.
- The system was re-charged yesterday with 500g of fluid and the appropriate amount of oil. Only 100g of fluid and 2g of oil came out, so could it be that the compressor's been running dry and is toast? No leaks detected with the vacuum test.
- The measuring blocks in VCDS show ON when AUTO is pressed, and OFF when ECON is pressed
- Air circulation flaps work fine, VCDS output test goes through without errors
- If I remove the connector on the AC radiator at the front, I get a code from the G65 sensor as I should. However, this doesn't affect the pressure reading in VCDS, so is there another pressure sensor somewhere?

My guess is either a bad pressure sensor, which is telling the car the pressure is rather high when it's not, and thus the compressor is running in free-circulation mode. As I understand, it's an always on type affair, and the climatronic only controls a valve in the system or the coolant fluid. Either that or the compressor is toast.
 
I'm leaning toward a stuck pressure valve on the compressor with this one. I did a scan of my A4 and that also shows pressure in the system even with the AC off. The pressure then rises by about 3-5 bar when the AC is turned on, and the current readings are more or less the same as on the A2.

My plan is to order the pressure valve, new condenser as the old one is pretty chewed up by road debris, and a pressure switch and change them all out at the same time.
 
If the G263 sensor is broken (code registered) the compressor will run at a lower rate. I remember someone saying about 30%. It's a temp sensor situated in the fresh air channel in your dash. Look up the master how to for pictures.
 
A short update: Turns out the replacement compressor fitted last year by the previous owner is not OEM or Denso, so I don't think I can swap out just the magnetic valve as I have no idea if the new valve will fit. I'm leaning towards getting a new Denso compressor for 295€ and I also noticed the condenser is badly damaged at the bottom, although not yet leaking so I'll change that, the receiver drier and and all the o-rings while I'm at it.
 
Another update: I had the system evacuated on Friday and had lost another 110g of fluid, so the system was definitely leaking. Turns out it was one of the dryer connections, which I discovered when changing the dryer, condenser, injection valve and the magnetic valve on the compressor. The result? Still no cold air! I'm thinking the leak had caused the compressor to run at full all the time and had eventually destroyed it. Now I need to order a new compressor and find a place who can do a proper flush of the system and install the new compressor. Not happy!
 
I'm thinking the leak had caused the compressor to run at full all the time and had eventually destroyed it.

That can't happen because as soon as the pressure gets below a certain point, the A/C will stop working, although the compressor will still turn (if it can). If the pulley still turns the compressor over, the compressor should be OK.

RAB
 
The compressor rotates fine and I can rotate it by hand. The pulley also feels solid and the center and the "ring" turn together. Seeing as it's a piston compressor with a swash plate, isn't it possible that one or more of the pistons have seized, preventing the plate from tilting and thus allowing the opposite side piston to compress the gas?
 
The compressor rotates fine and I can rotate it by hand. The pulley also feels solid and the center and the "ring" turn together. Seeing as it's a piston compressor with a swash plate, isn't it possible that one or more of the pistons have seized, preventing the plate from tilting and thus allowing the opposite side piston to compress the gas?

If one of the pistons was seized and preventing the plate from tilting, the remaining pistons would not be able to compress, or only to a minimal degree:

https://www.youtube.com/watch?v=DPuYF0eNK6M

RAB
 
This is what I gathered as well and I also found that same video on Youtube some time ago. What I think I will do is just double check I'm getting voltage at the compressor connector and if I am, I guess the only option is to replace the compressor.

Does anyone have a wiring diagram for the AAC / Climatronic unit showing the pinouts at the back?
 
Another update: I measured the voltage at the connector for the compressor regulating valve (N280) while the car was running, and I'm getting 10V. I also get a DTC when I disconnect the valve, so this also leads me to further believe the compressor is toast. I've now sent out RFQs to 5 different garages to see who can flush the system and change the compressor.
 
Another updated: I initially diagnosed the compressor incorrectly. After looking at the compressor carefully when the car was running I could see the center nut on the shat was not rotating with the pulley, meaning the coupling inside the pulley had sheared. I tried to turn the compressor with a ratchet from the shaft nut and no dice, completely seized.

I bought a new-used compressor from a 2008 1.4tdi Polo and it's going to be fitted tomorrow. The only difference seems to be the location of the electrical connector with the bracket being mounted to the top of the compressor instead of the end. This is not going to be a problem, the A2 harness is long enough for this new location as well. The part number for the Polo part matches that of the A2 according to ETKA.
 
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