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Radiator Fan Issues - Running on ignition - Help

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  • #16
    Originally posted by S2central.net View Post
    If you pull relays 3 or 11 (in the main fusebox) it should help trace the fault down.
    With both relays out and the fan still runs then you are looking at J135 or J155 misbehaving (or a wiring fault).
    If 3 is out it stops - Had to do that to see if after run pump was working (for 5 secs) on ignition (couldn't hear with fan going), and to use vagcom without the fan running! Ill do some other check tomorrow after work.

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    • #17
      Couple of easy things to do then - Relay 3 is Speed 1 (slowest) so its looped into the after-run circuit with J155 etc

      1. Swap relays 3 & 11 over to rule out possibility of relay 3 contacts being mechanically stuck ON
      2. Unplug J155 (after-run relay in the aux panel above driver pedals at position 14 - does that stop the fan running ?
      3. Assuming J155 removal stops the fan operation... plug it back in, then unplug the thermal switch (F98) on the water rail - does that stop the fan operation ?

      I know its tricky getting access to F98, but with care and some luck you should be able to slide one of the two spade terminals off the switch - thats enough to disconnect it. As an alternative, if you know how to extract the relevant pin (temporarily) from T8f then you can do it that way.
      Last edited by S2central.net; 9th July 2018, 23:05.
      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

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      • #18
        I have had a similar issue - was a damaged component on the after-run pump module (J155) circuit board - I replaced the component and all was well again.
        Worth popping the cover off the J155 and seeing if there is a burnt out component. I seem to remember someone on here helped me identify to component and it was documented on the forum for future reference

        Whilst we are on this subject, I have a question regarding pin 87a on the J155 - does the ECU control this pin in order to prevent the J155 from activating the after-run pump if the engine is running?
        If so does the ECU pull low when the engine is running or when it is not running?

        Panthero Coupé quattro 20vt
        Indigo ABY coupé
        Imola B6 S4 Avant

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        • #19
          I assume you mean pin 87b on J155 - thats a black/yellow wire on the ABY which does indeed connect with ECU on pin 41. I believe that is used to signal some kind of engine running status to J155 - I never did investigate if that is pulled to 12V, 0V or something else when engine running. I think the old 20VT SSP helps describe it - I would need to dig it out.
          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


          • #20
            Thanks Paul. Its interesting that the URS4 doesn't appear to utilize that pin, so it could well be unnecessary.


            Here we go, J155 / 324 repair info, just for reference.

            https://www.s2forum.com/forum/techni...control-module
            Panthero Coupé quattro 20vt
            Indigo ABY coupé
            Imola B6 S4 Avant

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            • #21
              Found a DE version of SSP143 on line. Describes it as an input function on the AAN from the climate control system so that doesn't fit with my theory :-(
              Attached Files
              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


              • #22
                And that SSP seems to align with ABY schematics for climate control - manual or digital - with the black/yellow wire connected at that red T5h plug. Need to investigate further as I otherwise don't know how is informed that the engine is running.
                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


                • #23
                  OK now I get it... Pin 87F on J155 is essentially the 'engine running' signal that comes from the fuel pump relay. Have a look at attached ABY schematic - J155 pin 4 (87F) is the red/blue wire that comes from track 59. That is Fuse 24 output which is only hot when the engine is running by way of the fuel pump relay - so J155 cannot activate when pin 87F is at 12V.

                  All of which means the connection from J155 to ECU pin 41 is a bit of a waste of time. The use of this pin 41 makes more sense on the aircon cars as a means of telling the ECU when the low speed fan is running and placing higher load on the engine... None of which explains why the ECU needs to know when that same rad-fan relay is engaged because of after-run duties via J155.
                  Attached Files
                  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

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