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    Thread: The "X" Circuit from the Ignition Switch.

    1. Member tolusina's Avatar
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      10-28-2013 05:28 PM #1
      The "X" Circuit from the Ignition Switch.

      What is "X"?
      "X" is the terminal of the ignition switch that's working while your car is starting and the headlights, wipers and HVAC fan go off.
      Here's a pic, hopefully it'll explain most all of the circuit.



      Understanding that circuit saves a whole lot of puzzlement [s]if[/s] when there's a failure of headlights, wipers and HVAC fan in various combinations.

      1st, lets follow the power flow through the schematic on a car with all systems good.
      Battery power is available to BOTH the ignition switch AND the switched circuit of the load reduction relay.
      Switch the ignition to the RUN position and power flows through the black/yellow wire activating the load reduction relay solenoid coil, making power available to the wipers, HVAC and rear defogger. At the same time, power is also switched directly to the headlight switch, which can then be switched to the High/Low beam dimmer switch.

      It is worth mentioning the parking/running lights at this point, they are on a completely separate circuit from the ignition switch and the "X" circuit, you've probably noticed that the parking/running lights work whether the key is switched on or not. Electrically, the parking/running lights have absolutely nothing in common with the headlight circuit even though the headlights and the parking/running lights are operated by the very same switch.

      There are several possible failure modes through the "X" circuit that are generally easy to diagnose fairly accurately just by the symptoms present.

      If everything downstream of "X" on the ignition switch, that is headlights, HVAC fan, wipers and rear defogger are all inoperative, it is reasonable to assume that "X" on the ignition switch itself has failed.
      There are several possible ways to test for this condition.
      The most conclusive way to test is to unplug the ignition switch and bridge battery power from the red battery power wire to the black/yellow "X" terminal wire, then check to see if all the downstream components are operative.
      Alternately, one could test for power at terminal 86 of the load reduction relay socket with the key switched on and the relay removed.
      One could also bridge the terminal 30 to the terminal 86 connectors at the load reduction relay socket with the relay removed and then check and see if the headlights work. Next bridge from terminal 30 to terminal 87 and see if the HVAC fan, wipers and rear defogger work.

      If the headlights work but the HVAC fan, wipers and rear defogger are inoperative, the load reduction relay itself is usually at fault. Put one hand on the load reduction relay and switch on the key, the relay should be felt to click on and then click off as a key is switched off. Bridging terminal 30 to terminal 87 will also verify that most of the rest of the circuit is good. Use a multimeter or a test light across terminals 85 and 86, there should be power showing whenever the key is in the wrong position. Don't confuse relay clicks from the fuel pump, glow plug or DigiFant power supply relay(s) for load reduction relay clicks.

      If the headlights do not work but the HVAC fan, wipers and rear defogger work, the problem is most likely in either the headlight switch or the high/low beam dimmer switch.
      It is also possible for the "X" terminal contacts in the ignition switch to be burned in such a way that adequate current will be available to operate the load reduction relay but adequate current to operate the headlights cannot flow. If this condition were present, I would expect the HVAC fan, wipers and rear defogger to operate normally, but they would probably switch off as the headlights were switched on.





      ---------
      Quote Originally Posted by kamzcab86
      I hate reading: "But I bought this car for $500 and don't want to put another dime into it."
      ____(hey, it's VW AND it's electrical, what's not to fail?) neoBentley+



    2. Member briano1234's Avatar
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      10-28-2013 05:50 PM #2
      Quote Originally Posted by tolusina View Post
      The "X" Circuit from the Ignition Switch.

      What is "X"?
      "X" is the terminal of the ignition switch that's working while your car is starting and the headlights, wipers and HVAC fan go off.
      Here's a pic, hopefully it'll explain most all of the circuit.



      Understanding that circuit saves a whole lot of puzzlement [s]if[/s] when there's a failure of headlights, wipers and HVAC fan in various combinations.

      1st, lets follow the power flow through the schematic on a car with all systems good.
      Battery power is available to BOTH the ignition switch AND the switched circuit of the load reduction relay.
      Switch the ignition to the RUN position and power flows through the black/yellow wire activating the load reduction relay solenoid coil, making power available to the wipers, HVAC and rear defogger. At the same time, power is also switched directly to the headlight switch, which can then be switched to the High/Low beam dimmer switch.

      It is worth mentioning the parking/running lights at this point, they are on a completely separate circuit from the ignition switch and the "X" circuit, you've probably noticed that the parking/running lights work whether the key is switched on or not. Electrically, the parking/running lights have absolutely nothing in common with the headlight circuit even though the headlights and the parking/running lights are operated by the very same switch.

      There are several possible failure modes through the "X" circuit that are generally easy to diagnose fairly accurately just by the symptoms present.

      If everything downstream of "X" on the ignition switch, that is headlights, HVAC fan, wipers and rear defogger are all inoperative, it is reasonable to assume that "X" on the ignition switch itself has failed.
      There are several possible ways to test for this condition.
      The most conclusive way to test is to unplug the ignition switch and bridge battery power from the red battery power wire to the black/yellow "X" terminal wire, then check to see if all the downstream components are operative.
      Alternately, one could test for power at terminal 86 of the load reduction relay socket with the key switched on and the relay removed.
      One could also bridge the terminal 30 to the terminal 86 connectors at the load reduction relay socket with the relay removed and then check and see if the headlights work. Next bridge from terminal 30 to terminal 87 and see if the HVAC fan, wipers and rear defogger work.

      If the headlights work but the HVAC fan, wipers and rear defogger are inoperative, the load reduction relay itself is usually at fault. Put one hand on the load reduction relay and switch on the key, the relay should be felt to click on and then click off as a key is switched off. Bridging terminal 30 to terminal 87 will also verify that most of the rest of the circuit is good. Use a multimeter or a test light across terminals 85 and 86, there should be power showing whenever the key is in the wrong position. Don't confuse relay clicks from the fuel pump, glow plug or DigiFant power supply relay(s) for load reduction relay clicks.

      If the headlights do not work but the HVAC fan, wipers and rear defogger work, the problem is most likely in either the headlight switch or the high/low beam dimmer switch.
      It is also possible for the "X" terminal contacts in the ignition switch to be burned in such a way that adequate current will be available to operate the load reduction relay but adequate current to operate the headlights cannot flow. If this condition were present, I would expect the HVAC fan, wipers and rear defogger to operate normally, but they would probably switch off as the headlights were switched on.





      ---------
      BIG THANK YOU RON..... You are so Marvelous....Don't get a big head now, well ok a little bit bigger

    3. Member tolusina's Avatar
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      10-28-2013 06:38 PM #3
      The quirk I forgot to include. It's curiously interesting, knowing about it can aid in quickly diagnosing issues with these circuits.

      Key in your pocket, switch the headlights, wipers and HVAC fan. None should run, park lamps should be on.

      Now pull and hold the headlight high/low beam switch on the turn signal stalk. Nothing happens? Release and pull it again.
      Every other pull of the high/low switch with the other switches on as described should result in the wipers and HVAC fan running as long as the high/low switch is held.

      Headlights should come on with every pull and hold, regardless is the other switches are on or not, headlights will be high beam only.






      .
      Quote Originally Posted by kamzcab86
      I hate reading: "But I bought this car for $500 and don't want to put another dime into it."
      ____(hey, it's VW AND it's electrical, what's not to fail?) neoBentley+



    4. Member kamzcab86's Avatar
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      10-28-2013 10:26 PM #4
      Nice explanation.

      I'd like to make a side note that for those who link to Cabby Info's electrical page along with the comment "check/test/replace the X relay", folks will not find "X Relay" listed... it is listed under its real name of Load Reduction Relay.
      Cabby-Info.com -- Your online guide to VW Cabriolets/Rabbit Convertibles
      Old Blue's Blog -- The adventures of a 1990 Westfalia
      "Fashion is a waste of money that could be better spent on, say, maintaining your car." ~James May

    5. Member grapedub4's Avatar
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      03-03-2014 10:57 PM #5
      what if my wipers work (only two settings is that normal?) and my headlights work but my HVAC does not. I turn the newly replaced switch to all 4 settings and nothing happens. I hear no clicking no nothing. I need atleast the fan to run

    6. Member briano1234's Avatar
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      03-03-2014 11:14 PM #6
      Quote Originally Posted by grapedub4 View Post
      what if my wipers work (only two settings is that normal?) and my headlights work but my HVAC does not. I turn the newly replaced switch to all 4 settings and nothing happens. I hear no clicking no nothing. I need atleast the fan to run
      Have you checked the ground wire on the motor connector side of the heater box drivers side, that ground can get fried and cause a no fan or intermittent fan operation.

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