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B7 A/C unit in B6 with Rear Demist Modification

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by Woorlord, Feb 8, 2010.

  1. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Feb 8, 2010]
    A B7 A/C unit will not work the Rear demist circuit in a B6 and does require a wiring loom modification with a 30A relay to get it to work. I have previously posted this but it was not so great to search for it, so have updated it with extra relay terminal info, which has recently been requested.

    The relay terminal numbers indicated below are for a standard 12v 30A Automotive relay, typicsl relays shown at this site Relay Schematic Here, you can use a 4-pin or 5-pin relay as terminal 87A is not used here.

    Relay coil is across terminals 85 & 87,
    Relay switch Common is terminal 30,
    Relay switch Normally Closed is 87A (No coil voltage and relay switch is connected normally between 30 & 87A),
    and
    Relay switch Normally Open is 87 (apply 12v to coil to make relay switch contacts between 30 & 87)

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

    Any B6/B7 A/C unit requires coding to the car VIN - talks to the Instrument cluster for security - I guess to stop people nicking and swapping these easily removed items as they will just pull out!!
    A/C removal - Single DIN is a doddle - just pull it out. Double DIN - I had to pull out & remove the radio and then I could pull out the A/C unit - Auto transmission lever needs to be pulled back twoards the handbrake first. Both instances no screws - they should pull out enough to remove the cables.

    VIN coding of the A/C unit can be done through VAG-COM - do have the procedure somewhere if required.

    A B7 A/C unit will not work the Rear demist circuit and does require a wiring loom modification with a 30A relay to get it to work. Thought I'd posted the modification but can't find it but have the text which is pasted below..............


    .............With the RNS-E out this gave me access to the "newer" A/C unit I had installed when going from Single to Double DIN.

    After mod. Rear Demist now comes on and the rear glass definitely gets warm - although I do notice that the relay pulses on and off and then on, say every 2-3 seconds. No errors with VAG-COM. Maybe it's the outside temperature being 20+ degrees? VAG-COM does register the relay switching on and off through monitoring the A/C unit, "channel 012", I seem to recall.

    Can't seem to get the heated wing mirrors on - but think they do not come on unless outside temp is 5 degrees or less. Today is 20+deg. They are actually controlled via the individual door modules - probably over CAN-BUS and not with this heated rear window circuit.

    Modification:

    Required for A/C units where Rear Demist is controlled by slave relay and not directly by internal switching of A/C unit. Bentley circuits suggest A4 models "from November 2004". I can confirm this mod is required for A/C unit part no. 8E0 820 043 BM.

    The mod. was pretty straight forward and required a four "blue" female spade crimps, a short length of 1.0mm wire and a 12v/30A automotive relay.

    Pull fuse F26 - Heated Rear Window - for safety!!

    Pull all plugs from A/C unit.

    Sourced a ground of A/C connector D13 - removed the hood casing - Soldered a wire here inside the plug and then remounted the casing. Terminated the free end in a female spade connector and this wire goes to the relay coil, terminal 86.

    Undo the taped loom wires to connector "F" - you need to pull back the tape around 2~3inches.

    Cut 4mm wire F6 (White/Lilac) around 1.5 inches back from "F" connector.

    • A/C end - soldered a "thinner" wire to this and terminate in a female spade connector which then goes to the relay coil, terminal 85. This is the control signal.
    • Car end - put a female spade connector on which goes to one side of the relay switch terminal 87. This is the feed to the heated window element.
    Cut 4mm wire F5 (White/Yellow) around 1.5 inches back from "F" connector.

    • A/C end - insulate as no longer used to supply 12V/30A to A/C unit.
    • Car end - (From fuse 226, i.e. Large 30A Fuse in position #26). Put a female spade connector on and wire goes to other side of relay switch, terminal 30.
    Re-taped all looms with PVC insulation tape.

    Refit all A/C unit plugs.

    Refit Fuse F26.

    Mod. Complete.

    I also cleared any DTC errors with VAG-COM - I tested at various stages to see if relay switched and the rear demist light would stay on before connecting the 12V/30A power feeds! Just to be 100% sure it was going to work!!

    Hope this helps.
    :rockwoot:
    Last edited: Feb 8, 2010
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  3. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Jun 19, 2010]
    Here is a circuit schematic on the modification.............
    [​IMG]
    #2
  4. Turkster
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    Turkster Bro.Paul 2.5TDI Quattro Sport

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    [Jun 20, 2010]
    ok, iv had this one, i presume your doing a upgrade as your old unit has got scratched to bugger?

    if so not all is lost,

    The unit itself comes in 2 parts, the face and the brains in the back, simply unscrew them and pull apart, use the nice new face on your old units brains at the back, then put them together and all should be well for you, like i said before, i had the same issue, is dead easy to do and can be done on the kitchen table in under 10 mins with care!
    #3
    JohnC likes this.
  5. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Jun 20, 2010]
    My reason for upgrading was part of a Single DIN to Double DIN conversion
    From what I've experienced the B7 unit offers better A/C control - perhaps newer firmware inside?
    #4
  6. rob irl tdi
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    rob irl tdi Member

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    [Jul 19, 2010]
    Ok I might be having this problem. Just the car and the rear demist wont work No codes in VCDS. I just bought a 2004 b6 sport. Looks like tea was spilled down the radio and maybe the climatronic was changed to one from a b7.

    Can anybody confirm if this part number is from a b7?. Here is part of my scanAddress 08: Auto HVAC Labels: 8E0-820-043.lbl
    Part No: 8E0 820 043 AA
    Component: A4 Klimaautomat 1324
    Coding: 00000Address 56: Radio Labels: 8E0-035-1xx-56.lbl
    Part No: 8E0 035 186 D
    Component: concert II GRO 0004
    Coding: 01001
    Shop #: WSC 63351
    VCID: 285432BBE29B
    1 Fault Found:
    00858 - Connection; Radio ZF Output to Antenna Amplifier
    36-10 - Open Circuit - Intermittent
    End ---------------------------------------------------------------------

    Shop #: WSC 63351
    VCID: 60C46A9BCA2B
    No fault code found.
    #5
  7. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Jul 19, 2010]
    When you operate the rear demist you will get an error message to the effect that the rear screen is will not switch short or open circuit - this would indicate you have a B7 A/C unit in a B6.

    example:
    [FONT=&quot]-------------------------------------------------------------------------------[/FONT]
    [FONT=&quot]Address 08: Auto HVAC Labels: 8E0-820-043.lbl[/FONT]
    [FONT=&quot] Part No: 8E0 820 043 BM[/FONT]
    [FONT=&quot] Component: A4 Klimaautomat 2833 [/FONT]
    [FONT=&quot] Coding: 00000[/FONT]
    [FONT=&quot] Shop #: WSC 00000 [/FONT]
    [FONT=&quot] [/FONT]
    [FONT=&quot]1 Fault Found:[/FONT]
    [FONT=&quot]00975 - Heated Rear Window (Z1) [/FONT]
    [FONT=&quot] 39-00 - Output won't Switch or Short to Ground[/FONT]
    [FONT=&quot]-------------------------------------------------------------------------------[/FONT]

    When there is a problem - the orange light for the rear demist button will turn on when the button is pressed and then turn off a second or so later and stay off.
    (I also seem to recall a b7 unit will also go to a lower cooling temperature., b6=18 degrees, b7=16 degrees.)

    The Radio aerial error you list above would suggest the radio has been switched on with the aerial disconnected.

    Suggest you reset all errors and then re-check all operations above and then re-scan with VCDS.
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  8. rob irl tdi
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    rob irl tdi Member

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    [Jul 19, 2010]
    I will clear it alright and scan again. I think my unit goes down to 16 degrees
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  9. rob irl tdi
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    rob irl tdi Member

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    [Jul 19, 2010]
    Cheers lads. Yea scanned it again and I have it coming up in VCDS as rear dimister no communications. So it must be a b7 unit.

    There is one button pealing on the unit. Any way of fixing it while I have it out to put the relay in? Can single buttons be bought seperate?
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  10. rob irl tdi
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    rob irl tdi Member

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    [Jul 26, 2010]
    So is there any way of fixing the peeling button?
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  11. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Jul 26, 2010]
    Buttons are not available separately from Audi.
    You could consider taking from another "donar" unit and fitting into your existing unit?
    #10
  12. rob irl tdi
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    rob irl tdi Member

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    [Jul 26, 2010]
    Then I would have to add a relay.. Maybe I might change

    Cna't get my avatar working
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  13. rob irl tdi
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    rob irl tdi Member

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    [Nov 9, 2010]
    I have seen two b6's now that go down to 16 degrees and there unit works the dimister

    My climate control 8E0 820 043 AA is from 01 to 04 so I think its orginal now even tho it goes down 16 degrees and that the problem is something else perhaps?

    I'm putting in my rsne and a different climate unit out of an o3 doublen din size
    #12
  14. mlody
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    mlody Member

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    [Nov 29, 2010]
    where could I obtain one of them relays? Are they all the same ? I mean if I go to a shop and say that I need a 12v 30 A fuse will that be the one?
    #13
  15. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Dec 5, 2010]
    Any reputable automotive shop should stock them - go to the shop and say, "Do you have a 12v 30A Automotive Relay Mr Shopkeeper!"

    Also available from Maplins - 40A rated one linked here.
    #14
  16. mlody
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    mlody Member

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    [Jul 15, 2011]
    i seem to have a problem. I installed my relay a couple of months ago and then a few weeks later my batter went flat. i took the aircon unit out and behind it i've seen melted wire (from the relay). I thought, the relay could have been faulty so today i went to change the relay and i just double checked all the wires. Connected everything up and turned the ignition on, pressed the button and listened out for the relay to kick in. It did, but after 3 seconds it went off again, then came back on and then went off again. It kept doing that non stop so i turned it off, also the 2 wires from terminal 30 and 87 heat up a good bit. What's the problem here?
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  17. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Jul 15, 2011]
    The relay switching on/off/on/off..... is normal. The "thick" wires will get warm owing to the amount of current the rear window element draws - the fuse is 30A.

    What was the rating of the original relay contacts you had, and did you test the old relay - i.e. had the relay contacts stuck together in the closed position thus keeping the rear window on all the time? This could have contributed to your battery drainage over time.

    Make sure the new relay is at least 30A rated, higher would be better in view of the constant on/off switching when the rear window is set to on.
    #16
  18. Cabbyfan
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    Cabbyfan Member

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    [Jul 15, 2011]
    My 02 plate Cab goes 18 degrees then LO .... drives me mad, I want 16 degrees ! Not that I use the climate much, sunshine means roof down woohoo :jump:
    #17
  19. mlody
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    mlody Member

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    [Jul 16, 2011]
    The old relay was perfect and I put that one back in but the wires have melted creating a short circuit so I got thicker wires now and let's hope for the best, but they are still heating up a good bit
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  20. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Jul 16, 2011]
    The "Load" carrying wires need to be at least the same size and rated cables - i.e. the wires across the relay switch (blue in my diagram) that feed the rear window - this is an absolute must or you risk your car bursting into flames!
    The signal wire from the A/C unit can be rated smaller as it is simply triggering the relay coil, (red in my diagram).
    #19
  21. fourcircle
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    fourcircle nj

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    [Aug 7, 2011]
    I just did this along with a double din conversion tonight. Thanks for the detailed instructions Colin.
    All went well except the concert 3 (i think it's a concert 3. double din CD player from a B7 A4) won't power on. I have a wiring loom for an RNS-E that I was under the impression would do the job for the concert until I decide whether i'm going to get an RNS-E or aftermarket hean unit. bugger

    edit*** I just had to add a pin in the block for +UB and run a wire to a power feed from SENS. Now I can have tunes while pondering what best to fill that double din space with next :)
    Last edited: Aug 8, 2011
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  22. fourcircle
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    fourcircle nj

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    [Aug 8, 2011]
    My new climate control unit is working without having to code it in VCDS. Rear demister is working well too. Is there any need to do any coding now?
    #21
  23. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Aug 8, 2011]
    Was it brand new - if so probably set to learn the VIN number from the instrument cluster.
    Are there any DTC errors?
    Has the A/C unit learnt the flap motor settings?
    Coding from Ross-tech site [see below] (probably 00000) - check the correct coding with what is set and what your car spec is.....

    Coding


    • 00?xx: Chassis
      • 0 = Sedan/Avant
      • 1 = Cabrio
    • 00x?x: Heated Windshield
      • 0 = Heated Windshield not installed
      • 1 = Heated Windshield installed
    • 00xx?: Sunroof
      • 0 = No Sunroof OR Normal Sunroof
      • 1 = Sunroof with Solar Cells


    Adaptation

    Channel 081: Vehicle Data Learning

    To start the process for vehicle data (VIN) learning, enter/save 26467 as new value.
    #22
  24. F33lings
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    F33lings New Member

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    [Apr 25, 2014]
    Hello guys,
    I saw that there are no reply's since a while on this topic.
    I have the same problem (rear defogger does not work) and thanks to you i'll try to fix this.
    cheers
    #23
  25. F33lings
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    F33lings New Member

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    [Apr 25, 2014]
    do you tried to buy stickers ?!
    #24

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