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  • Electrical wizards!? Anyone....

    I have a couple of electrical issues I would like to fix and if required, am happy to pay for someone to come to me (I have a large garage/tools etc) or I go the them - I can help and will do as requested (i.e take this apart etc). Issues are

    Radiator fans not working when car running - either speed. Changed rad switch, checked relays, swapped relays etc, swapped fuses, checked all fuses. After run system inc fan works fine (new pump and relay recently). I think this has been an issues since I bought the car in 2008 - I have only done 3000 mile since and always on clear roads.

    My miles left counter goes mental sometime and says I have 20 miles left when I have 3/4 tank! Usually sorts its self out but has been bugging me.

    I have a cruise control setup Id like fitted

    I'm just awful at wiring diagrams etc! Car is in great condition, no VAGCOM faults etc. Rad fan issue is most important, Cruise next and miles left is just annoying.

    The car is being detailed now and I am hoping to get to some shows/meets for the first time this year - However without fans I'm loathed to leave the safety of clear welsh roads where my temps stay low. A motorway crawl would be stressful, turning off to let after run system cool it is not ideal.

  • #2
    Well if you are sure about the health of all those things you have mentioned, the last link in the system is the resistor plate. As the fan is a single speed power is fed through the resistor plate to give the variable speed stages. It should be mounted on the inside of the inner wing or trace the fan wiring back. Its difficult to test accurately due to the low resistances involved so if you can get power up to the plate but none comes out then thats your problem. Might need to jumper the fan switch to get the power up to the plate. There is probably some info out there that might be of assistance at least on the principles!

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    • #3
      Scroll down to the fan speed stages and resistor section:
      http://www.sjmautotechnik.com/troubl...oling.html#fan

      Assuming that you have an ABY/ADU as the 3B uses a different system with a resistor and 2 speed fan.
      Last edited by twoqu; 2nd April 2019, 19:58.

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      • #4
        Hi Trist. You are a clever guy and I am sure you can fix this yourself. I used the excellent guide by UrS4Boy here to fix mine.
        https://forums.quattroworld.com/s4s6/msgs/21503.phtml
        I found three issues with mine.
        Poor connection at the two pin thermo sensor on the water rail;
        Faulty thermo sensor bottom of radiator;
        Faulty after run relay.
        If you work through the guide methodically and test all your circuits with a multi meter, its not too difficult.
        If you are still struggling in a couple of weeks, my car should have been painted and I will come over for a spin
        Nothelle S2 Avant in restoration

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        • #5
          http://www.s2central.com/S2_Schematics/B/B73-09.pdf

          Not sure what model year you have. Looks like the 2nd and 3rd speed stages are independent. So the 3rd speed stage is fed directly from the relay into the fan rather than through the resistor plate. The 2nd stage is fed through the resistor plate as is the 1st stage (afterun). So if that true the resistor plate cannot be responsible for both issues.
          If the afterun works then that implies the E1 thru E3 is intact at least.
          So the 2nd stage (normal speed) is operated trough the rad fan switch, which trips the 2nd speed relay which sends the power to the resistor plate E2 and out E3 to the fan.
          The 3rd stage (Jet roar) is also operated through the rad switch, which trips the 3rd speed relay which send full power to the fan.
          So at the rad switch we should have +12v ign on one terminal. The other terminals are for the respective fan switches. So with a piece of wire you need to connect the 12V to one or other of the other terminals which should cause the fan to work on either of the higher speeds. If nothing happens you need to work along the system to find the fault.
          First is identify the relay concerned. Is the signal from the switch reaching there? Is there power and earth on the other terminals . Is there continuity down to either the resistor pack or fan. Electrics of this sort is not really a black art. Its just a mater of elimination following the flow.
          Maybe I have oversimplified it, so if you have a specific question then ask.
          Last edited by twoqu; 2nd April 2019, 21:14.

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          • #6
            Have you checked the temperature of the bottom hose where it joins the bottom of the radiator ? If your thermostat is stuck closed or your rad is blocked then the rad switch won’t get hot enough to trigger the fan

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            • #7
              Not sure where it is located but it looks like there is a massive 60A fuse somewhere that seems to feed all the relevant relays involved in the fan operation. However if you have the afterrun fan speed that sort of shoots that theory down. Still would be useful to know where that it located.

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              • #8
                Originally posted by twoqu View Post
                Not sure where it is located but it looks like there is a massive 60A fuse somewhere that seems to feed all the relevant relays involved in the fan operation. However if you have the afterrun fan speed that sort of shoots that theory down. Still would be useful to know where that it located.
                since ive been poking aroung with wiring a lot lately,the onlt 60a fuse ive come across is clipped on to the far right side of the auxilliary relay panel near the bonnet release
                It's a love/hate relationship with the S2,i love it,it hates me

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                • #9
                  I don't know why the fuse box lid indicates various rad fan fuses. Apart from that 60A fuse, the only other fuse that has any influence is S15 which feeds the fan rad switch.
                  The 60A is battery fed (live constantly) presumably to operate the after run fan. The S15 is ign live.
                  Think these other relays are on the aux relay plate as well, so you are going to have to access them.

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                  • #10
                    Hi Simon. Yes I've had the bottom of the main rad (at fan swicth) to >100 degree C (checked with laser temp tool). Thermostat is new and works fine. Rads are perfect (been pressure tested, cleaned and painted. Rad switch is new from Audi. I will follow twoqus post - I really should have thought of bridging contact on the fan switch....

                    Originally posted by simons2 View Post
                    Have you checked the temperature of the bottom hose where it joins the bottom of the radiator ? If your thermostat is stuck closed or your rad is blocked then the rad switch won’t get hot enough to trigger the fan

                    Comment


                    • #11
                      Thanks for all the replies chaps.

                      twoqu - I will do as suggested! Cant believe I didn't think of bridging! And yes been under the drivers side lower panel. All fuses there are good and as per first post - I have a brand new 324 relay which means the after run system is faultless (tested). It can only be wiring to/from the resistor plate as twoqu suggests. Its being detailed at present, so not here, but I will report back once I have had another look.

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                      • #12
                        Thanks Dave - Appreciated. After run system is all perfect though (new parts and tested). Defo pop over - I know some great roads and photo spots! Going to do as twoqu suggests!

                        Originally posted by Tractor Dave View Post
                        Hi Trist. You are a clever guy and I am sure you can fix this yourself. I used the excellent guide by UrS4Boy here to fix mine.
                        https://forums.quattroworld.com/s4s6/msgs/21503.phtml
                        I found three issues with mine.
                        Poor connection at the two pin thermo sensor on the water rail;
                        Faulty thermo sensor bottom of radiator;
                        Faulty after run relay.
                        If you work through the guide methodically and test all your circuits with a multi meter, its not too difficult.
                        If you are still struggling in a couple of weeks, my car should have been painted and I will come over for a spin

                        Comment


                        • #13
                          Bridging the fan switch only simulates the activation of the two stages so all that removes is the fan switch itself, which as it is new/recent is unlikely to be the cause. It does allow us to trace the issue further up the line. Lets concentrate on the 1st stage (normal) fan speed as thats the most used one.
                          First you need to verify there is 12V with ign on at the rad switch connector. If not check fuse 15 either by measuring both sides of the fuse in situ by probing the exposed metal or removing it and testing it for resistance which should be 0.
                          If you have 12V then you need to bridge the connector from the 12V to the 1st stage rad fan terminal in the block. ( position 3 12V, position 2, 1ST speed, position 3, 2ND speed.). Once you have found the 12V you should be able to work out the rest!
                          Now when we turn the ign on we are simulating the rad switch temp for 1st stage fan. The switch wire goes to the 1st stage relay which I think is in the fuse box next to the spare fuses. When the relay is energised it sends power to the fan through the resistor plate at E2. Ideally you would test the relay plate for the rad switch signal, battery 12V, earth and continuity down to the resistor plate. Its difficult to probe down these contacts so you might need to butcher a suitable terminal to ensure connection.
                          If all those present and the relay is good, power should go to E2 on the resistor plate. So next you need to measure voltage at the E2 terminal it should be 12V. If not then the relay itself is suspect. If you have 12V at E2, measure the voltage at E3 which should be lower (10V?) as its pased through the resistor plate. No power out of E3 means the resistor is dead.
                          Of course you could get lucky and just bridge the rad switch and test for power at E2. If you have power at E2 and not at E3 then it has to be the resistor plate.
                          So you can either be systematic or take a stab at what you think the issue is!
                          The 2nd stage is a little less complicated but lets see if we can get the 1st working when you get the car back.
                          As I said it should be relatively simple to trouble shoot this with either ideally a multimeter or at worst a test light of some description.
                          Last edited by twoqu; 3rd April 2019, 15:54.

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                          • #14
                            I have a multi meter and will follow your simple instructions - Many thanks for taking the time to type them in

                            Car back with me this weekend so I will post an update then.

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                            • #15
                              If you need another there is a resistor plate on ebay at the mo
                              Nothelle S2 Avant in restoration

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