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  • #1

    Help with auto climate control, schematics?

    My automatic climate control has been blacked out on and off for about 6 months and it's driving me nuts as I have no fan or temperature control.

    The buttons that sits under and at the sides of the unit is lighting up but not the LCD's = it does nothing.

    I've measured my friends Audi 100 that has the same ACC system and my own in hope to find what's wrong, this is what came up:

    Audi 100:
    B1 4.93V

    C2 0.13V
    C3 10.92V
    C5 9.54V
    C6 12.20V
    C11 12.20V
    C13 12.15V
    C14 12.20V

    D9 12.30V
    D15 12.28V


    Audi S2:
    B1 4.95V

    C2 0.10V
    C3 0.06V
    C5 9.18V
    C6 0.01-0.04V (very dodgy connection)
    C11 11.82V
    C13 11.95V
    C14 11.99V

    D9 11.97V
    D15 11.83V



    So to sum things up these should be the bad guys:

    C3 0.06V
    C6 0.01-0.04


    What is C3 and C6 and where should I look?
    Or am I missing something obvious here?

    Thanks for any help I can get as I'm no good with electrics.


    [EDIT]
    This is a continuation of this thread,
    http://www.s2forum.com/forum/showthread.php?t=31742
    Audi S2 -1994 | 480 Hp 650 Nm | FlexFuel | MaxxECU | 3" Stainless | Porsche GT3 Front Brakes
    http://www.garaget.org/?car=52877
    Tags: None
  • #2
    I'll have a look - I appear to be the S2 electric guru this week

    An MY94 Coupe you say with the digital climate system... I have some factory diagnostics on that too but I'll check the wiring first.
    Paul Nugent
    Webmaster http://S2central.net
    Administrator http://S2forum.com

    1994 S2 Coupe ABY - aka Project Lazarus
    2001 A6 allroad 2.5TDi - family tank
    2003 S4 Avant 4.2 V8 - daily burble

    Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

    There are only 10 kinds of people that understand binary - those that do, and those that don't

    Comment

    • #3
      OK - some 1st spots... WIth reference to this ---> http://www.s2central.net/S2_Schematics/B/B75.PDF

      Look at Track 23 and you'll find pin D9 - this should be common to pin C3 (track 49 via 54) as it goes thru the low pressure switch F73 which I assume should be closed. Thats why C3 is different.

      Either the system has low pressure or that switch is faulty or disconnected - its on the evaporator housing in the cabin.

      Pin C6 is an odd one now - goes to the rev counter on the S2 - dunno why it would show ~12V on the Audi 100.
      Paul Nugent
      Webmaster http://S2central.net
      Administrator http://S2forum.com

      1994 S2 Coupe ABY - aka Project Lazarus
      2001 A6 allroad 2.5TDi - family tank
      2003 S4 Avant 4.2 V8 - daily burble

      Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

      There are only 10 kinds of people that understand binary - those that do, and those that don't

      Comment

      • #4
        There is a good sequence of diagnstic tests that can be run on the digital system - I'll need to dig it out - there's quite a tomb of it and its all paper ATM...
        Paul Nugent
        Webmaster http://S2central.net
        Administrator http://S2forum.com

        1994 S2 Coupe ABY - aka Project Lazarus
        2001 A6 allroad 2.5TDi - family tank
        2003 S4 Avant 4.2 V8 - daily burble

        Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

        There are only 10 kinds of people that understand binary - those that do, and those that don't

        Comment

        • #5
          Wow, thanks for your efforts Paul, I was kinda hoping you would reply.

          What is weird is why the low pressure switch would black out the LCD and therefor the heater fan and all of it's functions.
          Last year I changed the AC compressor to a refurbed one, it had about 1.400 miles on it and a couple of hoses and then got it refilled at my local AC go-to-guy.
          Worth noting is that before I fixed the AC compressor = no cooling medium present the unit still worked perfectly except the lack of cooling power.
          I hope you know what I mean by it's completely dead, I mean it's really dead. No life at all.
          This results in no fan and no chance to choose the desired temperature.
          The buttons is illuminated though.

          Yes, I know about the OBD system that ACC has, and when it worked the last time around I checked all the channels for faults or errors and _none_ was found.
          This is what's get me, when it works it has no stored faults and when it does not work I can't understand what is wrong.

          I wouldn't dare leave my car at a audi shop in fear of the bill and useless parts they probably would replace.
          Audi S2 -1994 | 480 Hp 650 Nm | FlexFuel | MaxxECU | 3" Stainless | Porsche GT3 Front Brakes
          http://www.garaget.org/?car=52877

          Comment

          • #6
            F73 is a safety switch - it prevents aircon from being used when there is no gas in the system... Not sure that would/should completely lock up the thing in that case - have you tried pulling the fuse(s) to force the head-unit into restart ?

            But is there still gas in it ?

            Is F73 working OK ?
            Paul Nugent
            Webmaster http://S2central.net
            Administrator http://S2forum.com

            1994 S2 Coupe ABY - aka Project Lazarus
            2001 A6 allroad 2.5TDi - family tank
            2003 S4 Avant 4.2 V8 - daily burble

            Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

            There are only 10 kinds of people that understand binary - those that do, and those that don't

            Comment

            • #7
              Oops, looked through my notes from the last time around again.

              Channel 52 - Faults or reasons that the AC compressor shuts down:
              e2: Low pressure in the system

              Channel 53 - Faults or reasons that parts or the whole ACC unit is not working
              f1: Radiator fan in stage 1 (I believe it refers to the one in the engine bay)
              a1: The fan for the inside temperature sensor

              Now, why the h**l would the ACC turn it self off because of these things, it should just kill the snow flake symbol (AC compressor).
              Weird, weird.
              Audi S2 -1994 | 480 Hp 650 Nm | FlexFuel | MaxxECU | 3" Stainless | Porsche GT3 Front Brakes
              http://www.garaget.org/?car=52877

              Comment

              • #8
                Originally posted by S2central.net View Post
                F73 is a safety switch - it prevents aircon from being used when there is no gas in the system... Not sure that would/should completely lock up the thing in that case - have you tried pulling the fuse(s) to force the head-unit into restart ?

                But is there still gas in it ?

                Is F73 working OK ?
                Yes I know it is a safety switch, but it does not explain how the ACC could work without coolant before, and I have never heard of such a thing preventing the ACC to control the heater matrix fan, it should just shut off the AC compressor.

                Yes, I have checked all fuses and pulled them several times.

                I will have to check for gas again, how do I check that F73 is OK?
                Audi S2 -1994 | 480 Hp 650 Nm | FlexFuel | MaxxECU | 3" Stainless | Porsche GT3 Front Brakes
                http://www.garaget.org/?car=52877

                Comment

                • #9
                  Bridge F73 closed and you should see 12V on C3 - it might make a difference. Your head-unit could be FUBARd but it would be sad to blame it without getting some fault codes out of it.

                  Paul
                  Paul Nugent
                  Webmaster http://S2central.net
                  Administrator http://S2forum.com

                  1994 S2 Coupe ABY - aka Project Lazarus
                  2001 A6 allroad 2.5TDi - family tank
                  2003 S4 Avant 4.2 V8 - daily burble

                  Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

                  There are only 10 kinds of people that understand binary - those that do, and those that don't

                  Comment

                  • #10
                    DOn't forget the fresh air blower (V2) is controlled by the head-unit... So if its unhappy/dead then no fan in the cabin !
                    Paul Nugent
                    Webmaster http://S2central.net
                    Administrator http://S2forum.com

                    1994 S2 Coupe ABY - aka Project Lazarus
                    2001 A6 allroad 2.5TDi - family tank
                    2003 S4 Avant 4.2 V8 - daily burble

                    Purveyor of HomeFries and Exclusive agent for Samco hose kits (S2/RS2)

                    There are only 10 kinds of people that understand binary - those that do, and those that don't

                    Comment

                    • #11
                      I know that the head unit is not knackered as they work in the Audi 100, he even bought one of me since I bought one extra hoping it would cure the problem but it behaves the same as soon as it gets into my car.

                      Will try bridging the F73 tomorrow and measure C3.

                      So if I try and unplug the cabin fan would the head unit wake up then?
                      Would be weird if it is the fan because it has never played up before, no suspect noises or anything but **** happens I guess.
                      Audi S2 -1994 | 480 Hp 650 Nm | FlexFuel | MaxxECU | 3" Stainless | Porsche GT3 Front Brakes
                      http://www.garaget.org/?car=52877

                      Comment

                      • #12
                        I bridged the F73 connector today, and the only result was that the fan started going on ignition.

                        Tried pushing the valve that sits on the same rail and there was pressurized gas/oil coming out.

                        Never had a chance to measure C3 again since the garage had some not so welcome night guests last night, and they "borrowed" my toolbox and multimeter.
                        ******..
                        Audi S2 -1994 | 480 Hp 650 Nm | FlexFuel | MaxxECU | 3" Stainless | Porsche GT3 Front Brakes
                        http://www.garaget.org/?car=52877

                        Comment

                        • #13
                          Well it's acting up again and I'm still clueless as what it could be.

                          Attaching pictures, outer temp lcd just shows three bars and ACC lcd is blacked out.
                          Buttons still illuminated however.

                          If anyone has any ideas or BTDT I am desperate to hear them.
                          Attached Files
                          Audi S2 -1994 | 480 Hp 650 Nm | FlexFuel | MaxxECU | 3" Stainless | Porsche GT3 Front Brakes
                          http://www.garaget.org/?car=52877

                          Comment

                          • #14
                            Have you tried reading the codes with a diagnostic?

                            Comment

                            • #15
                              Automatic Climate Control Diagnostics and Repair

                              Originally posted by k.alle View Post
                              Well it's acting up again and I'm still clueless as what it could be. Attaching pictures, outer temp lcd just shows three bars and ACC lcd is blacked out. Buttons still illuminated however. If anyone has any ideas or BTDT I am desperate to hear them.
                              Got your PM. I have never had an issue with the Automatic CC head unit in my 93 UrS4 so all I can give you is second hand info that others have posted. Good luck with it.

                              The schematics I know of are posted below.

                              DieselDes posted this link before re: Climate control repair. I think you need to have a look at it. Your black screen could just be burned out bulbs (or it could be more serious). http://www.audiworld.com/tech/elec153.shtml

                              Climate Control Diagnostics:
                              http://12v.org/urs/Climate%20Control...0&%20Codes.pdf





                              RS2'd 93 UrS4 5 spd sedan
                              94 UrS4 V8 6 spd manual avant

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