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My AUX Fan Wiring Idea - need opinions and assistance

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    My AUX Fan Wiring Idea - need opinions and assistance

    OK, so while sitting at work today, when I'm about 5 days away from taking off for school, I've gotten to thinking about to best way to wire up my AUX fan.


    Here's what I had originally planned:
    I purchased a 30A relay, bunch of 18ga wire, little switch and a red LED. I was going to wire in my relay, using the switch and the low temp setting on the radiator switch, and make it simple - in-line fuse, etc etc. Well, I thought, why not reuse the car's fuses and relays already there, right? Just tap into the current wires.

    Something I've thought of is a way to still use the stock relays for the stock AUX fan. even though mine is not stock, it can still run off of the same circuit, I think. By that, I mean run off of the temp switch and everything, while I wire in my own switch that will override the temp switch and run high no matter what.

    Basically, there would be no need for my RadioShack relay, since I would use the car's relays to run my fan.


    So, here's what I'm thinking now:
    First, I'll wire my fan up to the stock car's wiring harness. For the full-speed voltage lead, I'll just send it into the 12v for the fan. For the low speed voltage lead, I'll use the resistor from the stock AUX fan, and then tap into the 12v for the fan. This would make it run slower - correct?

    At this point, it should run like the stock AUX fan did - low speed at 91 C and high speed at 99 C, whilst utilitizing the stock 15A and 30A fuses and respective relays for low and high. Now on top of this, I would like to wire in a single rocker switch that will turn the fan on high no matter what. To do this, couldn't I just tap into the high-speed switch wire from the TEMP switch - this would click on the high speed relay and run the fan at high. What happens if the temp switch turns on the low speed relay. Will that really matter? Since electricity follows the path of least resistance, won't the slower-speed circuit (since it has that inline resistor) pretty much be ignored, even though it'd be on? It couldn't blow the fuse since the resister is there, correct?

    Now, for my LED, I'd like it to turn on whenever the fan is on. Don't care if it's the switch or automatically - I want it on when the fan is on. I may wire it to the low speed and high speed individually to notify me when it's on high or low. Can you put a resister in line to an LED and run it dimmer - or will the LED just not light up? To get my LED to light up, couldn't I just run a wire from the 12v into the fan? Even though the fan may pull up to 30A, that shouldn't matter for the LED, right? It won't be pulling that current to the LED, correct?

    Also - a question regarding the temp switch. This acts as a switch, correct? What I mean by that is, there's 12v going into the switch, then, dpending on the temp, the temp switch will send the 12v to either the low speed relay or the high speed relay. In my case, if the switch it on, the high speed relay will remain on - and that shouldn't cause an issue if the low speed relay switches on too, right?


    I know this is probably REALLY confusing. But basically, here's what I need to know:
    1. How do I wire my own switch into the stock AUX fan setup to run high all the time (even if the fan switch wants to run the fan on low_. When off - it should act as if there's nothing there - and run low/high respectively.
    2. Can I tap the 12v line going into the fan to light up my LED to show me when the fan is running?
    3. Does the temp switch operate by sending 12 volts to either the low or high speed relays?


    So...does this make a whole lot of sense to anyone? lol

    Let me know what you all think!



    By the way - for those wondering, I got a 16in electric fan with curved blades for about $60 shipped off ebay about a year ago. Unsure of brand, but pretty sure it moves at least 2500 CFM, maybe even 3000.
    - Sean Hayes

    #2
    fuck, you had to post this idea after i got my new fan wiring all nice and neat. I guess i could still use the stock fan wiring to drive the relay? the maker of my 3300cfm fan recomeds 10ga wire

    Comment


      #3
      just do it

      Comment


        #4
        Originally posted by e304me
        fuck, you had to post this idea after i got my new fan wiring all nice and neat. I guess i could still use the stock fan wiring to drive the relay? the maker of my 3300cfm fan recomeds 10ga wire
        If it doesn't pull more than 30A, it should be fine. That's the fuse that BMW uses, and I'm sure they wouldn't run more current than a wire has a fuse for.
        - Sean Hayes

        Comment


          #5
          Originally posted by kylebes1
          just do it
          So - my ideas won't fry anything then? lol I'm not thinkin they would, but I wanted to run them by someone first.
          - Sean Hayes

          Comment


            #6
            yeah go wire it up. I want to know if the low speed and stuff works

            Comment


              #7
              Originally posted by e304me
              yeah go wire it up. I want to know if the low speed and stuff works
              Haha, I'll probably tackle it tomorrow. Need to hardwire my V1 too. Anyone know what wire I can tap for a 12v lead with ignition on down below the cluster?
              - Sean Hayes

              Comment


                #8
                the ignition switch? you should just do a little plug in on the roof though, and tap it to the power sunroof if you have one

                Comment


                  #9
                  Originally posted by e304me
                  the ignition switch? you should just do a little plug in on the roof though, and tap it to the power sunroof if you have one
                  Don't have power sunroof. And I wanted to run the wire from the dash so I could hook up a hidden display later on.
                  - Sean Hayes

                  Comment


                    #10
                    theres 3 wires going to the stock fan? and i cant get it out of the car! operation tin snip may have to begin shortly

                    Comment


                      #11
                      Yep, there are three wires going into the stock aux fan. One is the ground, one is the low speed and one is the high. It should be right behind the driver's side headlights.
                      - Sean Hayes

                      Comment


                        #12
                        well are you sure the low speed isnt part of the fan then?

                        and yeah i know where the connector is, it just seems like the bumper will have to come off to get the fan out. I put mine on the rad, but would still like to get it out

                        Comment


                          #13
                          Originally posted by e304me
                          well are you sure the low speed isnt part of the fan then?

                          and yeah i know where the connector is, it just seems like the bumper will have to come off to get the fan out. I put mine on the rad, but would still like to get it out
                          Yea, you have to remove the radiator or the front bumper to get it out. It's unfortunate.

                          You got your fan to fit as a puller? I could not get my fan on that side at all!
                          - Sean Hayes

                          Comment


                            #14
                            well i have a smaller engine. I think im going to try to seal the spaces between the rad and condensor, so that the AC will work a little bit better at low speeds

                            is the stock fan worth anything? becaue im about to chop mine into little peices to get it out

                            Comment


                              #15
                              Hi Sean.

                              OK, so as far as wiring, you have the right idea. Using a toggle to trigger the stock high speed relay will work perfect, and cannot backfeed the low speed resistor...if it does, the relay is still open, so there is no circuit to complete.

                              Your fan on LED is a good idea, but may I suggest 2 things:
                              1. Use a incandescent bulb. 12 volts is easier than fugging around with LED's.
                              2. Do 2 bulbs, one for high, one for low.

                              RadioShack has little housings with or without bulbs, easy install.

                              Go for it!

                              Luke

                              Closing SOON!
                              "LAST CHANCE FOR G.A.S." DEAL IS ON NOW

                              Luke AT germanaudiospecialties DOT com or text 425-761-6450, or for quickest answers, call me at the shop 360-669-0398

                              Thanks for 10 years of fun!

                              Comment

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