Aux heating is "kaputt" - but what exactly?

   #1  

core

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Hello,

I'm struggling to diagnose and repair Webasto auxiliary heating in the car. Since it's a rare piece of extra equipment, I have trouble finding a good mechanic and source of info to help with diagnosing.

Progress so far:
  • First, the aux heating didn't want to start anymore, was throwing error also on the dashboard MFD
  • Other related symptoms were:
    • Engine slow to warm up (both water and oil temperature), unless driving uphill, or on motorways
    • Water and oil temp dropping if idling or driving slowly (city, downhill, suburban roads)
    • Normally the temps are water bang at 90º C and oil between 80-105º C, but now unless driving uphill or on motorways (110+ km/h), oil stays between 65-75º C and is not at steady temp
  • Error codes were the following:
Code:
01410 - Heater Over-Temp
            000 - - - Intermittent
             Freeze Frame:
                    Fault Status: 00100000
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 89
                    Time Indication: 0

             Freeze Frame:
                        After-Run
                    Temperature: 148.0°C
                    Temperature: -48.0°C
                    Voltage: 12.00 V

01411 - Temperature Sensor (G18)
            007 - Short to Ground - Intermittent
             Freeze Frame:
                    Fault Status: 00100111
                    Fault Priority: 3
                    Fault Frequency: 2
                    Reset counter: 86
                    Mileage: 252297 km
                    Time Indication: 0
                    Date: 2015.05.08
                    Time: 12:57:28

             Freeze Frame:
                        Malfunction
                    Temperature: 205.0°C
                    Temperature: 0.0°C
                    Voltage: 12.00 V

02251 - Heater Unit Locked
            000 - - - Intermittent
             Freeze Frame:
                    Fault Status: 00100000
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 89
                    Time Indication: 0

Went to my VW mechanic who first replaced the DSG temperature sensor, which was apparently also kaputt (and he also unlocked the heater, cleared the fault codes). This seemed to work for a few days, the driving temperatures of water/oil were back to normal, but while Webasto aux heating was "working" (it turned on and completed the 20 min heating cycle), the air inside the cabin was not hot enough - it was lukewarm at best. Meaning, something was still causing an issue. And after a few days, Webasto was locked again, same faults as the first time (above).

Another service visit, where they replaced the G18 temperature sensor (new OEM part, 1K0815111A). Cleared the fault codes and unlocked the heater unit again. Voila, now also the aux heating was working as it should, resulting in a warm car after 20 mins. But it only worked for a few days and now the same thing: Webasto is locked, only this time there are just two error codes:
Code:
2 Faults Found:
01410 - Heater Over-Temp
            000 - -
             Freeze Frame:
                    Fault Status: 01100000
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 122
                    Time Indication: 0

             Freeze Frame:
                        After-Run
                    Temperature: 148.0°C
                    Temperature: -48.0°C
                    Voltage: 12.07 V

02251 - Heater Unit Locked
            000 - -
             Freeze Frame:
                    Fault Status: 01100000
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 122
                    Time Indication: 0

I have no idea what's causing the issues now, it seems that for some reason the aux heating overheats, but the question is why? Could the VW wizards please point me into the direction how can I diagnose this with output tests and measuring blocks to determine which component(s) should be checked?

FWIW this error was present for quite a while (maybe ever since I had the car) and didn't seem to impact the aux heating, but at this point, I'm willing to consider any option.
Code:
9477489 - Motor for Air Distribution Flap
          B109D 71 [008] - Actuator stuck

Below is a full, fresh auto-scan, and PR codes at the bottom. FWIW the car is stock, without modifications, except of few safe-minor VCDS tweaks that shouldn't be related since this seems to be a hardware issue.
Code:
Tuesday,26,January,2021,19:32:43:33127
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 20.4.2.0 (x64)  HEX-V2 CB: 0.4513.4
Data version: 20200730 DS317.0
www.Ross-Tech.com


VIN: VSSZZZ7NZFVxxxxxx   License Plate:
Mileage: 255100km-158511mi   Repair Order:



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Chassis Type: 7N-VW36 (7N0)
Scan: 01 02 03 08 09 10 15 16 17 18 19 20 25 2E 42 44 46 4C 52 53
          55 56 61 62 65 72 76 77

VIN: VSSZZZ7NZFVxxxxxx   Mileage: 255100km-158511miles

01-Engine -- Status: OK 0000
02-Auto Trans -- Status: OK 0000
03-ABS Brakes -- Status: OK 0000
04-Steering Angle -- Status: OK 0000
08-Auto HVAC -- Status: Malfunction 0010
09-Cent. Elect. -- Status: OK 0000
10-Park/Steer Assist -- Status: OK 0000
15-Airbags -- Status: OK 0000
16-Steering wheel -- Status: OK 0000
17-Instruments -- Status: OK 0000
18-Aux. Heat -- Status: Malfunction 0010
19-CAN Gateway -- Status: Malfunction 0010
20-High Beam Assist. -- Status: OK 0000
25-Immobilizer -- Status: OK 0000
2E-Media Player 3 -- Status: OK 0000
42-Door Elect, Driver -- Status: OK 0000
44-Steering Assist -- Status: OK 0000
46-Central Conv. -- Status: OK 0000
4C-Tire Pressure II -- Status: OK 0000
52-Door Elect, Pass. -- Status: Malfunction 0010
53-Parking Brake -- Status: OK 0000
55-Headlight Range -- Status: OK 0000
56-Radio -- Status: OK 0000
61-Battery Regul. -- Status: OK 0000
62-Door, Rear Left -- Status: OK 0000
65-Tire Pressure -- Status: Not registered 0011
72-Door, Rear Right -- Status: OK 0000
76-Park Assist -- Status: Cannot be reached 1100
77-Telephone -- Status: OK 0000
-------------------------------------------------------------------------------
Address 01: Engine (J623-CFFB)       Labels:. 03L-906-018-CFF.clb
   Part No SW: 03L 906 018 HM    HW: 03L 906 018 M
   Component: R4 2.0l TDI   H28 9980 
   Revision: 44H28---    Serial number:               
   Coding: 001D003A042401080000
   Shop #: WSC 01286 386 08256
   ASAM Dataset: EV_ECM20TDI01103L906018HM 003013
   ROD: EV_ECM20TDI01103L906018F_VW36.rod
   VCID: 7CA1F518A663719B0EB-8028

No fault code found.
Readiness: 0 0 0 0 0

-------------------------------------------------------------------------------
Address 02: Auto Trans        Labels: 02E-927-770.clb
   Part No SW: 02E 300 062     HW: 02E 927 770 AL
   Component: GSG DSG AG6     521 4002 
   Revision: 05652104    Serial number: 00001406061628
   Coding: 0000020
   Shop #: WSC 44551 111 44551
   VCID: 52FD7BA058E757EBB47-8006

No fault code found.

-------------------------------------------------------------------------------
Address 03: ABS Brakes        Labels: 7N0-614-109.clb
   Part No SW: 7N0 614 109 S    HW: 7N0 614 109 S
   Component: J104   C3 450M VD7C 0040 
   Revision: --H07---    Serial number: 00000008322492
   Coding: 0027518
   Shop #: WSC 00020 790 00000
   VCID: 3D27381CF179B893795-8068

No fault code found.

-------------------------------------------------------------------------------
Address 08: Auto HVAC (J301)       Labels:| 3C8-907-336.clb
   Part No SW: 7N0 907 426 CC    HW: 7N0 907 426 CC
   Component: AC Manuell    H20 0607 
   Revision: 00001004   
   Coding: 0010004003
   Shop #: WSC 00020 999 00000
   ASAM Dataset: EV_ACManueBHBVW36X A01010
   ROD: EV_ACManueBHBVW36X_VW36.rod
   VCID: 77ABEA349F4552C3639-8022

1 Fault Found:
9477489 - Motor for Air Distribution Flap
          B109D 71 [008] - Actuator stuck
          Intermittent - Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Status: 00000001
                    Fault Priority: 2
                    Fault Frequency: 6
                    Reset counter: 162
                    Mileage: 254860 km
                    Date: 2021.01.24
                    Time: 11:53:54


-------------------------------------------------------------------------------
Address 09: Cent. Elect. (J519)       Labels:. 1K0-937-08x-09.clb
   Part No SW: 5K0 937 086 Q    HW: 5K0 937 086 Q
   Component: BCM PQ35 M    122 0174 
   Revision: BC122001   
   Coding: 60180A3BE9251AC4C08800C8500089EC477D9388626D2D626484C72000C1
   Shop #: WSC 00020 790 12345
   VCID: 42DD4BE08487C76B047-8016

   Subsystem 1 - Part No SW: 7N1 955 119 A    HW: 7N1 955 119   Labels: 1KX-955-119.CLB
   Component: WWS    140605  033 0044
   Serial number:         140625221228
   Coding: 004DBD

   Subsystem 2 - Part No SW: 5Q0 955 559     HW: 5Q0 955 559   Labels: 5Q0-955-547.CLB
   Component: RLS  024 0042
   Serial number: Y14M03D18H23M45S27S7
   Coding: 0728DD

No fault code found.

-------------------------------------------------------------------------------
Address 10: Park/Steer Assist (J791)       Labels:| 3AA-919-475.clb
   Part No SW: 3AA 919 475 S    HW: 4H0 919 475 E
   Component: PARKHILFE PLA H06 0043 
   Revision: --------    Serial number: 56201419300487
   Coding: 14830A
   Shop #: WSC 00020 999 12345
   ASAM Dataset: EV_EPHVA2C000000000 002014
   ROD: EV_EPHVA2C000000000.rod
   VCID: 4BC366C4B34D0623F71-801E

No fault code found.

-------------------------------------------------------------------------------
Address 15: Airbags (J234)       Labels:| 5K0-959-655.clb
   Part No SW: 7N0 959 655 C    HW: 7N0 959 655 C
   Component: VW10Airbag002 H13 0014 
   Serial number: 003LGPES9JMS
   Coding: 003032
   Shop #: WSC 00020 999 00000
   ASAM Dataset: EV_AirbaVW10TS6VW428 A01004
   ROD: EV_AirbaVW10TS6VW428.rod
   VCID: 3FDB4214F7F5AA836B9-806A

   Crash sensor for side airbag: driver side:
   Subsystem 1 - Part No SW: ---            HW: ---       
   Component: S.Sens.Fahr.V  --- --- 
   Serial number: 3493ETS607729281ADD$
   Coding: 000000

   Crash sensor for side airbag: front passenger side:
   Subsystem 2 - Part No SW: ---            HW: ---       
   Component: S.Sens.Beif.V  --- --- 
   Serial number: 3503ETS60CA3A281A9D.
   Coding: 000000

   Crash sensor for side airbag: rear: driver side:
   Subsystem 3 - Part No SW: ---            HW: ---       
   Component: S.Sens.Fahr.H  --- --- 
   Serial number: 3513ETS60783C281A9DX
   Coding: 000000

   Crash sensor for side airbag: rear: passenger side:
   Subsystem 4 - Part No SW: ---            HW: ---       
   Component: S.Sens.Beif.H  --- --- 
   Serial number: 3523ETS60A128281ADDT
   Coding: 000000

   Crash sensor for front airbag: driver side:
   Subsystem 5 - Part No SW: ---            HW: ---       
   Component: F.Sens.Fahr  --- --- 
   Serial number: 35540TS600A581B1ADDN
   Coding: 000000

No fault code found.

-------------------------------------------------------------------------------
Address 16: Steering wheel (J527)       Labels:| 5K0-953-569.clb
   Part No SW: 5K0 953 501 CR    HW: 5K0 953 569 AL
   Component: LENKS.MODUL   016 0140 
   Revision: FF010042    Serial number: 20140722200410
   Coding: 1992240000
   Shop #: WSC 00020 999 00000
   ASAM Dataset: EV_VW360SteerWheelUDS A03004
   ROD: EV_VW360SteerWheelUDS.rod
   VCID: 7CA1F518A663719B0EB-8028

   Multifunction steering wheel control module:
   Subsystem 1 - Part No SW: 1P0 959 538 B    HW: 1P0 959 538 B  Labels: 3C8-959-537.CLB
   Component: E221__MFL-TAP  H02 0103
   Coding: E30000

No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments (J285)       Labels:| 5K0-920-xxx-17.clb-SRI1
   Part No SW: 7N5 920 870 L    HW: 7N5 920 870 L
   Component: KOMBI         H03 0905 
   Serial number: 00000000000000
   Coding: 141F01
   Shop #: WSC 00020 999 00000
   ASAM Dataset: EV_Kombi_UDS_VDD_RM09 A04727
   ROD: EV_Kombi_UDS_VDD_RM09_004_VW32.rod
   VCID: 40D941E88A0BD57B123-8014

No fault code found.

-------------------------------------------------------------------------------
Address 18: Aux. Heat        Labels: 1K0-815-007.clb
   Part No: 7N0 963 272 E
   Component: Standheizer     044 4941 
   Revision: 00044000    Serial number: 09028239000000
   Coding: 0031132
   Shop #: WSC 00020 790 00000
   VCID: 372B2A34D34592C3A39-8062

2 Faults Found:
01410 - Heater Over-Temp
            000 - -
             Freeze Frame:
                    Fault Status: 01100000
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 122
                    Time Indication: 0

             Freeze Frame:
                        After-Run
                    Temperature: 148.0°C
                    Temperature: -48.0°C
                    Voltage: 12.07 V

02251 - Heater Unit Locked
            000 - -
             Freeze Frame:
                    Fault Status: 01100000
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 122
                    Time Indication: 0


-------------------------------------------------------------------------------
Address 19: CAN Gateway (J533)       Labels:. 7N0-907-530-V2.clb
   Part No SW: 7N0 907 530 AQ    HW: 7N0 907 530 AL
   Component: J533  Gateway H58 1653 
   Revision:   H58       Serial number: 170714F1003254
   Coding: 468202
   Shop #: WSC 00020 790 12345
   VCID: 7F5B0214B7F56A832B9-802A

2 Faults Found:
01327 - Control Module for Parking Aid (J446)
            004 - No Signal/Communication
             Freeze Frame:
                    Fault Status: 01100100
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 115
                    Mileage: 254780 km
                    Time Indication: 0
                    Date: 2015.06.15
                    Time: 13:55:26

01044 - Control Module Incorrectly Coded
            000 - -
             Freeze Frame:
                    Fault Status: 01100000
                    Fault Priority: 1
                    Fault Frequency: 117
                    Reset counter: 255
                    Mileage: 254780 km
                    Time Indication: 0
                    Date: 2015.06.15
                    Time: 13:55:22


-------------------------------------------------------------------------------
Address 20: High Beam Assist. (J844)       Labels:. 8K0-857-511.clb
   Part No SW: 7N0 857 511 P    HW: 8P0 857 511 C
   Component: FLA           H04 0012 
   Revision: AA001002   
   Coding: 0201816B74745D545420363E01
   Shop #: WSC 00020 790 00000
   VCID: 40D941E88A8BD57B123-8014

No fault code found.

-------------------------------------------------------------------------------
Address 25: Immobilizer (J334)       Labels:| 5K0-920-xxx-25.clb
   Part No SW: 5K0 953 234     HW: 5K0 953 234
   Component: IMMO          H03 0905 
   Serial number:               
   Coding: 000000
   Shop #: WSC 00000 000 00000
   ASAM Dataset: EV_Immo_UDS_VDD_RM09 A03710
   ROD: EV_Immo_UDS_VDD_RM09_VW31.rod
   VCID: 6A8DC340DCF7FF2BEC7-803E

No fault code found.

-------------------------------------------------------------------------------
Address 2E: Media Player 3
Cannot be reached

-------------------------------------------------------------------------------
Address 42: Door Elect, Driver (J386)       Labels:. 7N0-959-793.clb
   Part No SW: 7N0 959 793 G    HW: 7N0 959 793 G
   Component: TSG FA        H03 0553 
   Revision:             Serial number: 0000109741843
   Coding: 01110720D400411011
   Shop #: WSC 00020 790 12345
   VCID: 46D557F0A8AFFB4B28F-8012

No fault code found.

-------------------------------------------------------------------------------
Address 44: Steering Assist        Labels: 5N1-909-144.clb
   Part No SW: 5N1 909 144 R    HW: 5N1 909 148 J
   Component: J500__APA-BS KL.324 1401 
   Revision: 1BH04739    Serial number: 00141890389801
   Coding: 0000258
   Shop #: WSC 00020 790 00000
   VCID: 41DF44EC8D81DC731DD-8014

No fault code found.

-------------------------------------------------------------------------------
Address 52: Door Elect, Pass. (J387)       Labels:. 7N0-959-792.clb
   Part No SW: 7N0 959 792 G    HW: 7N0 959 792 G
   Component: TSG BF        H03 0553 
   Revision:             Serial number: 0000109123241
   Coding: 01110520DE00411011
   Shop #: WSC 00020 790 12345
   VCID: 45D750FC95A9F053215-8010

2 Faults Found:
02127 - Exterior Door Handle Light / Mirror Light
            012 - Electrical Fault in Circuit
             Freeze Frame:
                    Fault Status: 01101100
                    Fault Priority: 3
                    Fault Frequency: 1
                    Reset counter: 115
                    Mileage: 254780 km
                    Time Indication: 0
                    Date: 2015.06.15
                    Time: 13:55:05

02119 - Potentiometer for Vertical Mirror Adjustment
            012 - Electrical Fault in Circuit - Intermittent
             Freeze Frame:
                    Fault Status: 00101100
                    Fault Priority: 3
                    Fault Frequency: 1
                    Reset counter: 160
                    Mileage: 254988 km
                    Time Indication: 0
                    Date: 2015.06.18
                    Time: 10:05:14


-------------------------------------------------------------------------------
Address 53: Parking Brake        Labels: 3AA-907-801.clb
   Part No SW: 3AA 907 801 J    HW: 3AA 907 801 J
   Component: J540 EPB4  VW-63206 0012 
   Revision:   H19       Serial number: 00000000177048
   Coding: 0024167
   Shop #: WSC 00020 790 00000
   VCID: 38292908DE5B9DBBAA3-806C

No fault code found.

-------------------------------------------------------------------------------
Address 55: Headlight Range (J745)       Labels:. 5M0-907-357-V3.clb
   Part No SW: 5M0 907 357 F    HW: 7L6 907 357 C
   Component: AFS-ECU       H04 0111 
   Revision: --------    Serial number: --------------
   Coding: 068200000B000000
   Shop #: WSC 00020 999 39850
   ASAM Dataset: EV_HeadlRegulVWAFSPt 002016
   ROD: EV_HeadlRegulVWAFSPt_VW32.rod
   VCID: 372B2A34DFC592C3A39-8062

   Left_headlamp_power_output_stage:
   Subsystem 1 - Part No: 1T0 941 329 B  Labels: 3D0-941-329.CLB

   Right_headlamp_power_output_stage:
   Subsystem 2 - Part No: 1T0 941 329 B  Labels: 3D0-941-329.CLB

No fault code found.

-------------------------------------------------------------------------------
Address 56: Radio (J503)       Labels:. 5M0-035-1xx-56.clb
   Part No SW: 3C8 035 195 F    HW: 3C8 035 195 F
   Component: RCD510        H02 5017 
   Revision: -----17S    Serial number: VWZ4Z3M1116057
   Coding: 0100040004000D
   Shop #: WSC 01357 011 00200
   VCID: 2B030644130D2623D71-807E

No fault code found.

-------------------------------------------------------------------------------
Address 61: Battery Regul. (J840)       Labels:. 1K0-907-534.clb
   Part No SW: 7N0 907 534     HW: 7N0 907 530 AL
   Component: Batt.regelung H58 1653 
   Serial number: 170714F1003254
   Coding: 030F1859
   Shop #: WSC 00020 790 12345
   VCID: 71BFD42CF1A10CF3ADD-8024

   Subsystem 1 - Part No SW: 1K0 915 181 H    HW: 1K0 915 181 A
   Component: J367-BDM  H07 0180
   Serial number: 41195A19581491546317

No fault code found.

-------------------------------------------------------------------------------
Address 62: Door, Rear Left (J388)       Labels:. 7N0-959-794.clb
   Part No SW: 7N0 959 794 G    HW: 7N0 959 794 G
   Component: TSG HL        H04 0553 
   Revision:             Serial number: 0000111223839
   Coding: 010005200000411001
   Shop #: WSC 00020 790 00000
   VCID: 47CB5AF4AFA5E243D39-8012

No fault code found.

-------------------------------------------------------------------------------
Address 65: Tire Pressure (J502)       Labels:. 1K0-937-08x-65.clb
   Part No SW: 5K0 937 086 Q    HW: 5K0 937 086 Q
   Component: RDK           122 0821 
   Coding: 018705
   Shop #: WSC 12345 123 12345
   VCID: 42DD4BE08487C76B047-8016

2 Faults Found:
01521 - Sensor for Tire Pressure
            004 - No Signal/Communication
             Freeze Frame:
                    Fault Status: 01100100
                    Fault Priority: 4
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 252459 km
                    Time Indication: 0
                    Date: 2015.05.10
                    Time: 21:11:26

01487 - System Function Test
            005 - No or Incorrect Basic Setting / Adaptation
             Freeze Frame:
                    Fault Status: 01100101
                    Fault Priority: 6
                    Fault Frequency: 1
                    Reset counter: 50
                    Mileage: 252459 km
                    Time Indication: 0
                    Date: 2015.05.10
                    Time: 21:11:26


-------------------------------------------------------------------------------
Address 72: Door, Rear Right (J389)       Labels:. 7N0-959-794.clb
   Part No SW: 7N0 959 794 G    HW: 7N0 959 794 G
   Component: TSG HR        H04 0553 
   Revision:             Serial number: 0000111229794
   Coding: 010005200000411001
   Shop #: WSC 00020 790 00000
   VCID: 47CB5AF4AFA5E243D39-8012

No fault code found.

-------------------------------------------------------------------------------
Address 76: Park Assist (J791)       Labels:| 3AA-919-475.clb
   Part No SW: 3AA 919 475 S    HW: 4H0 919 475 E
   Component: PARKHILFE PLA H06 0043 
   Revision: --------    Serial number: 56201419300487
   Coding: 14830A
   Shop #: WSC 00020 999 12345
   ASAM Dataset: EV_EPHVA2C000000000 002014
   ROD: EV_EPHVA2C000000000.rod
   VCID: 4BC366C4B34D0623F71-801E

No fault code found.

-------------------------------------------------------------------------------
Address 77: Telephone (J412)       Labels:| 5N0-035-729.clb
   Part No SW: 5N0 035 729 E    HW: 5N0 035 729 E
   Component: TELEFON       H07 0593 
   Revision: 1B001001    Serial number: 00007666453106
   Coding: 0A10000080010101
   Shop #: WSC 00020 999 12345
   ASAM Dataset: EV_UHVUMI 001007
   ROD: EV_UHVUMI.rod
   VCID: 323D1B2034A777EB947-8066

No fault code found.

End----------(Elapsed Time: 01:34, VBatt start/end: 12.2V/12.2V)-----------


 
   #2  

downtime

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I would almost most certainly say it's the webasto's water pump that is acting up. The over heating error code indicates to this direction as well. The water is not circulating for sure as the temps are not rising.

Look here for pointers how to change it : https://blog.lausdahl.com/2011/12/vw-touran-webasto-thermo-top-v-water-pump-renewal/

If I remember correctly there are vcds output tests in webasto controller. You should be able to test if the water pump is running with those.
 
   #3  

kevinm

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My first guess would be the water pump like downtime. If the pump turns out to be fine, check the heater matrix. I retrofitted webasto on our mk6 golf. A few months ago, we had low heat output and it was a blocked heater matrix. We had no fault codes though.
 
   #4  

Spacewalker

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Heater locked because over temp - for safety
unlock and do output test first and then measure blosk for peroper temp
then do Run-in and look for data if they are nortmal, shlod load up to 95%
 
   #6  

core

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Many thanks everyone for your quick answers. Perhaps a dumb question, but how do I know that the Webasto water pump is operating correctly? There is a sound coming from front right wheel area when I start the output test, but do I need to be checking measuring blocks (and which ones) and other parameters in order to determine it's operating as intended? FWIW the mechanic said "the pump is working", but given he doesn't have a lot of practical experience with stock Webasto aux heating (mostly from my car, hehe), I am a bit skeptical, and wouldn't want to rule anything out.

But given it's another 100 € + labor costs (and I already spent 200+ for both sensors and labor costs, and a lot of wasted time), I would like to be at least somehow sure first the pump is indeed faulty before replacing it.
 
Last edited:
   #7  

downtime

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VCDS output test should be able to test the pump functionality, you should be able to turn on the pump and listen if it's working or not. But it is clear that as the webasto is overheating and it's shutting down due to that, there's no water circulating in the heating chamber. So either the water pump is not working or the other option what was mentioned above could be blocked heater matrix.
That is a bit trickier to verify though.

Oh and also what Spacewalker wrote. Use VCDS to check the measurement blocks for webasto. What does it show as flame temperature, water temperature etc.
 
   #8  

golfi_vend

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Hehe...yes. Blocked Matrix. I've replaced so many failed pumps and only diagnosed 1 blocked core(customer didn't order replacement), so I totally forgot that.

You may want to try bypassing core with some pipe like I did and run webasto again.
 
   #9  

core

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Thanks again, @downtime and @golfi_vend. I'll run those tests and report back.

Another thing: could it be that the Webasto heater unit itself has some issues during the combustion/heating phase, that there is something wrong during the burning process inside the heating chamber (eg. faulty injector) which increases the temperature too much, causing it to shut down? Presumably this "heating/combusiton issue" wouldn't necessarily show up as an error code. This is a suggestion coming from my mechanic since he once had a similar case on another VW car.
 
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core

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Quick update, it looks like that indeed the pump might be acting up. Previously when I ran the tests there was an audible sound coming from the front right wheel with the V55 recirculating pump test started. Yesterday it was silent, so my guess is it might be working intermittently. The only other variable might have been the ambient temperature above 5º C, but I would expect that when someone runs a test, this condition is ignored, and the water pump should start regardless.

Have ordered the aux. water pump and will report back once replaced. Thanks again for everyone's help.
 
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