2013 Superb, pre-FL.  CFFB engine, DSG, Climatronic

 

I've been fighting with the recirculate servo on and off for a few months now.

 

Symptom:

- Driving and all the windows fogged up

- VCDS scan, says the servo is jammed and the position sensor is short to earth

- Swapped servo (AKA positioning motor for recirulate flap, it's a PITA to swap on RHD cars as there is a bolt wayyy up the back), no change

- Swapped climatronic controller, no change

- Continuity test on all 5 relevant connections from the servo plug end to the clima plug end, wiring is fine and no shorts or opens

- Drive servo with 12V, watch potentiometer with a multimeter, it goes through it's range OK with no spikes or shorts.

- Drive servo with 12V, measuring blocks on VCDS.  It goes from 40 to about 200 (which is within the range that I assume is 0-255) with no spikes that I see

- Drive servo through it's range to see if it sticks, doesn't seem to (plus I've tried a servo not mechanically connected to anything too)

- The 5V supply to the servo potentiometer is fine, no spikes (I watched it on a DSO)

- The GND connection to the servo potentiometer is fine

- The wiper connection to the servo potentiometer is NOT shorted to earth, not at the servo end, not at the clima end.

- Basic settings, both from VCDS or by holding down "face vent + AC button" does not perform the test for the recirc servo, but all the other servos do their tests

- Clearing the codes, the error usually comes back immediatley

 

About the only thing I haven't changed is the actual wiring loom itself so I guess that's the next step.  Given that the loom goes all over the place, I'll just replace the actual 3 wires that connect to the potentiometer.

 

I'm hoping some of the cluey people here have a better idea.

Address 08: Auto HVAC (J255)       Labels:| 5K0-907-044.clb
   Part No SW: 3T0 907 044 BS    HW: 3T0 907 044 BS
   Component: Climatronic   H19 0607  
   Revision: 00001007    
   Coding: 0010000002
   Shop #: WSC 33361 790 00999
   ASAM Dataset: EV_Climatronic A01010
   ROD: EV_ClimaAutoBasis_SK46.rod
   VCID: 040C23548F60CD6403-8050

3 Faults Found:
9472881 - Motor for Fresh Air / Recirculated Air Flap 
          B108B 71 [009] - Actuator stuck
          Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 12
                    Mileage: 127565 km
                    Date: 2018.07.28
                    Time: 00:08:00

9472882 - Motor for Fresh Air / Recirculated Air Flap 
          B108B 54 [009] - Missing Calibration / Basic Setting
          Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 12
                    Mileage: 127565 km
                    Date: 2018.07.28
                    Time: 00:08:00

9476881 - Position Sensor for Fresh/Recirculated Flap Motor 
          B109B 11 [008] - Short to Ground
          Intermittent - Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 2
                    Fault Frequency: 5
                    Reset counter: 52
                    Mileage: 127565 km
                    Date: 2018.07.28
                    Time: 00:08:00

 

 

 

CLIMA.pdf

OK so in the end it was a couple of things:

1) The wire from the pot wiper in the servo to the clima module was faulty.  Even though it passed the continuity tests, once I replaced it the error was able to be solved.  Possibly the problem was with the connector, once plugged in the connection may have been faulty however when not plugged in it tested fine.

 

I replaced the wire with a 000 979 009E repair wire.  In the attached diagram above, it was the gr/gn wire.

 

2) The end stop learning (basic settings) cannot be done without the servo mounted in the air box.  I was performing it with a second servo just floating in the air.  It seems that was contributing to the 'short to earth, short to positive' errors when the potentiometer hits the endstops.  It seems that the clima module expects the servo to drive the flap to the end and then stall (the learning bit).  If the servo doesn't stall before the pot reaches the limits, then the basic settings fails and the 'missing calibration / basic setting' error is returned.

 

Anyway, working now.  Hope this helps someone in future.