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Wiring an additional electric fan switch, need some thoughts

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    Wiring an additional electric fan switch, need some thoughts

    So a few months ago I did some extensive work on the M20 and removed the stock fan clutch and put in a 16'' SPAL puller. Works great- used a 80c thermo switch and wired it up using the stock Aux High-speed fan wiring.

    All is well about it, but I have been wanting to wire in another switch that I can force the fan to turn on- rather than waiting for 80c. I've drawn out what I am planning to do- tested it and it works. Just not sure if it is in my best bet to splice and tap into the lines before the thermo switch.

    Planning on splicing in before the thermo switch and retrofitting an old defroster switch to turn the aux fan on. Could also use a 30A switch (drawn)- I know this carries 12v but not sure really what amperage the .75ga bk/br and gn/bk wire carries- its just signal right? The 4ga bk/bu carries the actual fan power.

    Is this ideal? Or should I somehow tap into the high speed relay #86 and use a dedicated ground?

    Note: I have nothing going through the normal speed relay- the fan is set to run only on HIGH through the stock high speed relay

    555Garage - Kingston, PA

    '13 BMW e70 X5 35d
    '95 BMW e34 525i
    '92 BMW e30 325i S52 Vert (Quade the Vert)
    '92 Range Rover Classic
    '90 Range Rover Classic
    '89 BMW e30 325i Coupe (The DIRTY30)
    '81 VW MK1 Rabbit Caddy Diesel
    '76 Honda CB550K Cafe/Brat
    '67 Pontiac LeMans
    '24 Model T Depot Hack
    ....And a bunch of Motobecane, Puch, Garelli, Batavus and Honda 49cc-78cc Mopeds...


    #2
    The switch like you have drawn is the easiest solution. All it does is turn on a relay, so the amperage draw is low. Run two wires from the terminals on the temp switch to the switch in the car and you're done.

    Defroster switch probably won't work though. It's more than just a switch on the inside (circuitry to control heated glass). Better off using a fog light switch, it's just a switch.

    Comment


      #3
      Awesome- just the answer I needed. I just wanted to be sure that the amperage is low enough that I don't need to have anything else in line.

      I actually took apart a defroster switch, removed the resistors, extra pins and stuff and now have a switch that is only ON/OFF with two pins. Took some acetone to the logo, so now it's just a boring (non-lit) black switch- so all is good.

      Thanks!!
      555Garage - Kingston, PA

      '13 BMW e70 X5 35d
      '95 BMW e34 525i
      '92 BMW e30 325i S52 Vert (Quade the Vert)
      '92 Range Rover Classic
      '90 Range Rover Classic
      '89 BMW e30 325i Coupe (The DIRTY30)
      '81 VW MK1 Rabbit Caddy Diesel
      '76 Honda CB550K Cafe/Brat
      '67 Pontiac LeMans
      '24 Model T Depot Hack
      ....And a bunch of Motobecane, Puch, Garelli, Batavus and Honda 49cc-78cc Mopeds...

      Comment


        #4
        Used a rear defrost switch, also got an old one that was green(pre 86)
        1989 Cirrus Blau coupe Racing Dynamics wheels and a Volvo Spoiler.

        Comment


          #5
          Well my defroster switch hack job wasn't the best. Got a fog light switch- no modification necessary :)
          555Garage - Kingston, PA

          '13 BMW e70 X5 35d
          '95 BMW e34 525i
          '92 BMW e30 325i S52 Vert (Quade the Vert)
          '92 Range Rover Classic
          '90 Range Rover Classic
          '89 BMW e30 325i Coupe (The DIRTY30)
          '81 VW MK1 Rabbit Caddy Diesel
          '76 Honda CB550K Cafe/Brat
          '67 Pontiac LeMans
          '24 Model T Depot Hack
          ....And a bunch of Motobecane, Puch, Garelli, Batavus and Honda 49cc-78cc Mopeds...

          Comment

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