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Radiator Fan Issues - Running on ignition - Help

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  • Radiator Fan Issues - Running on ignition - Help

    Firstly apologies - I'm not great with electrics, please bear with me. I have read a thread on here regarding fans running full time https://www.s2forum.com/forum/techni...nstantly-s2-93 etc - however mine is running when I turn the ignition on, and stays on whilst the car is running. Switch ignition off it stops.

    Its a 1993 non AC ABY Avant

    I've checked all the fan relays and they seem fine
    I've run the test of the after-run system and that fires up on ignition for 5 seconds as it should so assume the 324 relay is good.
    I've tried another rad temp sender

    Will the 2 blade sender on the water manifold that you cant really get to without taking the rad out cause this? Any ideas appreciated. Or anyone nearby fancy taking a look for me for beers / notes?

  • #2
    Afterrun fan circuit only works with engine and ignition off. Your fault lies in the speed 2 and 3 function. Disconnect the wiring from the fan switch at the base of the radiator - your fan will probably stop. Measure the resistance on the fan switch. A low reading means you need to replace the switch.
    Mike

    http://www.s2-audi.co.uk

    Comment


    • #3
      Yep - go after the thermal switches at the bottom of the rad first... those determine which of the two main fan relays are activated (speed 2 or speed 3). Its possible a relay is stuck on - or the switch wiring is shorting. I do recall the wiring down there is dirty & brittle so care is advised when pulling off connectors etc

      The 2-pin thermal switch in the water rail is only for the after-run activation (the water recirculation pump combined with fan speed 1).
      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
        Cheers both. Ill get onto this tomorrow and report back.

        Comment


        • #5
          Originally posted by Mikes2 View Post
          Afterrun fan circuit only works with engine and ignition off. Your fault lies in the speed 2 and 3 function. Disconnect the wiring from the fan switch at the base of the radiator - your fan will probably stop. Measure the resistance on the fan switch. A low reading means you need to replace the switch.
          Hey Mike - Unplugging the fan switch in the radiator made no difference, fan still runs on ignition. I have re-tested all the relays on the bench and they function perfectly. The rad fan switch itself - I tested what I thought is 'ohms' and get low reading, but that is the same on about 8 spare rad switches I have from other audis so assume I'm doing something wrong rather than they are all dead?

          Comment


          • #6
            Originally posted by S2central.net View Post
            Yep - go after the thermal switches at the bottom of the rad first... those determine which of the two main fan relays are activated (speed 2 or speed 3). Its possible a relay is stuck on - or the switch wiring is shorting. I do recall the wiring down there is dirty & brittle so care is advised when pulling off connectors etc

            The 2-pin thermal switch in the water rail is only for the after-run activation (the water recirculation pump combined with fan speed 1).
            Hi Paul - See my post above. Would it suggest a wiring fault? Oh I've PM'd re wiring diagrams on B3s

            Comment


            • #7
              check the resistor pack and associated wiring
              Mike

              http://www.s2-audi.co.uk

              Comment


              • #8
                Attached is a little 8-page primer with the schematic marked up and a lot of notes to help anyone fault finding this circuit. I did it quite quickly so please forgive any typos, but do let me know if you find serious errors. By following the logic of this - pretty simple relay stuff - you can quickly find ways to isolate faults in specific relays, but a basic multimeter will be very useful for any tests.
                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


                • #9
                  Another note to add with regards that 'engine running only' pin onto J155 is the corner case where it gets activated by the ECU for a few seconds (via the T5h plug which tracks to pin 41 on the ECU) when the ignition is turned on - this is why you hear the after-run water pump being tested for a few seconds - all part of the control circuitry inside J155.
                  Last edited by S2central.net; 9th July 2018, 13:01.
                  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
                    Originally posted by Trist28 View Post

                    Hey Mike - Unplugging the fan switch in the radiator made no difference, fan still runs on ignition. I have re-tested all the relays on the bench and they function perfectly. The rad fan switch itself - I tested what I thought is 'ohms' and get low reading, but that is the same on about 8 spare rad switches I have from other audis so assume I'm doing something wrong rather than they are all dead?
                    This possibly means you have a short circuit on the wiring plug to the radiator fan switches. That is a 3-pin plug and with ignition ON, you should only see 12V at pin 3 (blue/red wire). With the connector unplugged from the switches it would be worth testing for volts at pins 1 and 2 (relative to battery 0V). If you understand the schematic, a short circuit between pins 1 & 3 on that plug would be same as F18 switch being closed and your fan will run at 2nd speed.
                    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
                      Originally posted by Mikes2 View Post
                      check the resistor pack and associated wiring
                      What and where is the resistor pack?

                      Comment


                      • #12
                        Front left corner down near the horns. Its maybe 15cm long and 3cm wide. It has three reasonably hefty connectors on it - do not mix them up if checking, cleaning etc.
                        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


                        • #13
                          It sits below the washer bottle attached to the chassis on an ABY. It's blue in colour about 4" long
                          Mike

                          http://www.s2-audi.co.uk

                          Comment


                          • #14
                            Originally posted by Mikes2 View Post
                            It sits below the washer bottle attached to the chassis on an ABY. It's blue in colour about 4" long
                            OK great - I know what you mean - For some reason I thought that was for the blowers in the car

                            Comment


                            • #15
                              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).
                              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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