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    Just wanted to say thanks to the OP. All the info in this thread made my 16 inch pusher fan install a breeze.

    Also, went with MZ3 radiator, 16 inch FFD 3000 cfm fan and utilized factory Aux fan wiring harness with new resistor and new stock temp switch. S50 sits at 11 o'clock while idling and if left idling it will very slowly creep to just past 12 on the cluster gauge and then the fan kicks on for about 30 seconds on low and brings it right back down to 11 position. Running it as a pusher in front of AC condenser.

    Comment


      Has anyone had any issue wiring in an electric fan to their stock Aux High speed relay/wiring and have an issue blowing a fuse only when the fan is engaged and the ignition is turned off?

      Running a SPAL puller, using stock aux fan high relay. I think the fuse/relay gets a power bump when it is engaged and engine is running then the engine shuts off. Basically coming straight off of alternator power.

      I'm thinking of now running a stand alone relay/fuse to the fan and temp switch. This way it will not be dependent on the iginiton +12v and will keep running when the car is turned off and hits the 80c thermo switch. Also, this will help since I've noticed that when the fan kicks on for a short period of time and the engine is turned off (coolant temp still =>80c) if you restart the engine it has hesitation since the coolant temp sensor (on thermostat to DME) is saying that coolant temp is too hot to turn on the engine again.

      Just an FYI since someone else might have had this issue
      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


        I need some help here,let see what you guys think:

        I've recently swapped my car for an euroS50 and deleted the clutch fan as there is not much space there.

        I picked up a citroen C5 pusher that only has two wires (RED/BLACK) so I spliced the original A/C connector and connected the RED to the green and BLACK to brown so it will turn on when I push the snowflake button.

        Worth to mention that I am running a M3 e36 radiator and normally I have no need of turning on the fan as the car runs quite cool while moving (85/90C--185/195F)

        But when I step on it,drifting or hillclimbing,even with the fan on, the car overheats a little,yesterday I saw the gauge mark 100C(212F) after few hairpin drifts.

        I am also hearing that relay sound every 5 seconds when the fan is on.

        By now,the fan is only being actuated manually.

        I was thinking about upgrading the radiator to an aluminum one or maybe drilling some little holes on the thermostat(stock one)

        what you guys think? thanks a lot for the support!

        cheers from basque country!
        “Speed has never killed anyone, suddenly becoming stationary… that’s what gets you.”
        ― Jeremy Clarkson
        Euro 318is M50 build thread

        Comment


          Chiming in here with my modified electric fan setup.

          Short story: I followed this DIY on how hook directly to the Aux fan wiring with a 80C switch. Easy to do, simple and not a lot of electrical cabling. I was running a SPAL 16'' Puller as my primary cooling fan for a few months.

          This worked like a charm- except under the ONE scenario: If the temp switch kicks on the fan at 80C and starts cooling, and I was ready to park or turn off the car and the fan was still on- the fan would obviously lose power. IF I had to turn the car back on for whatever reason (maybe to move the car after you parked it) and the temp was still over 80C- the startup of the ignition I would blow the stock 30A aux fan fuse every time. I found out that this can happen when switching from the +12v of the battery (ignition ON but engine OFF) to the new +14.3v you get from turning over the engine and obtaining the power bump from running from the Alternator. By the way- I never blew the in-line fuse I added from the +12v of the fan- only the 30A fuse in the fusebox.

          Also- which is a great point on why I modified it- was that say you are getting ready to pull into your destination, you might be idling a bit to find parking etc etc and the car gets up to 80C. The fan kicks on and might still be running when you turn the car off. Which is fine. But if you need to turn the car back on again, the thermo switch on the thermostat- which goes to the DME- will tell the DME that the engine coolant is too hot and don't supply fuel. So you get this hesitation when trying to start up. I can't get a definite temperature of what the thermostat DME switch reads that tells the engine that it is too hot. I only found out what resistance it reads at certain temps. If you know- I would really be interested what this threshold is.

          Anyway- my plan was to remove the fan from the Aux wiring fuses/relay and run power directly to a new relay that has constant +12v w/o the ignition on. First tried to wire up a new relay and fuse to the stock fusebox. Wasted my time since I couldn't find the correct female blade inserts for the fusebox. Decided to do a completely standalone setup.

          Here is what I used and how I wired it in:

          Hella 30A Relay and weather proof wiring harness $15
          - Relays are pretty much all the same from what I found. Went with this one since I decided on mounting it stand-alone from everything else and tried to make the install clean. Sure you can use a standard Autozone 30A relay, but finding the wiring harnesses are hard to find locally and at the end it will probably be a pretty messy wiring job. Installed mine on the side of the fuel pump relay cover.


          30A In-Line fuse holders $4/each
          - Used this instead of using the Accessory fuse holder (some have used this stock fuse holder for other things) Put one from the +12v Constant coming out of this stock fuse holder to terminal 30 on the relay. Used the other one for the +12v for the fan.

          Here is my drawing and relay layout.





          Relay Wiring
          Terminal 30: +12v (12GA wire) constant from stock accessory fusebox (with In-line 30A fuse)
          Terminal 85: Ground (12GA wire)
          Terminal 86: Trigger switch (14/16GA wire) I'm using my 80C thermo switch with a manual override switch that I used a extra fog light switch and mounted it next to the defrost/hazards (to turn on the fan under 80C if needed) You need to tap into a 7.5 fuse that has constant +12v so fuses 21, 22 and 23 are always on. I tapped fuse 21 (NOT 10 as pictured) since it is used for other switches on the car. Run a wire from here, to the thermo switch. Then a second wire back to Terminal 86.
          Terminal 87: Fan +12v (12GA wire) used an in-line fuse here to protect the fan. Mounted it near the fusebox for easy access.
          Terminal 87A: NOT USED (unless you need power to something that is ALWAYS on and OFF when the fan is ON)

          Notes:
          Make sure you invest in good butt connectors, crimp (or solder if you prefer) and electrical wrap. I hate glossy electrical tape, so I purchased some premium wire wrap.

          Thats about it! It's not the most complex job, but it gets it done and doesn't rely on anything stock. Hopefully this will help out people who might see the same issues. There are a few threads around that I've read about their fans blowing fuses left and right. This should be the solution. Good luck!!
          Last edited by Klug; 06-03-2015, 10:48 AM.
          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


            Question - I have a 16 inch pusher fan wired in on the factory aux fan wiring harness. Just this past weekend the low speed circuit quit working and jumping the terminal would not engage low speed. High speed circuit works. Relays swapped with no change. All fuses good and swapped with others to double test with no change. Checked continuity on black wire to fuse box and low speed wire has continuity.

            Aux fan does engage when you press the snowflake button... Does this mean the diode in the fuse box is bad?

            A bit stumped by this one as temp switch is good and resistor is good as well. Even swapped in a new resistor with same results.

            Comment


              Very weird if snowflake fires aux fan. Usually diode being fried prevents fan from firing when snowflake is pressed...

              and thanks klug, added to first post!

              Check Us out on Facebook
              Needing a harness adapter or wiring help? Check it out: also have 24v motor mounts, E30 M3 covers and E36 ECU mounts!
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              Comment


                Why is this not a sticky yet?

                Comment


                  I have an M50nv.

                  After reading through this, I am stuck between ordering the 3 pin 80/88 to retain the 2 speed OEM fan functionality vs. ordering the 82* 2 pin for the fan to kick on high right away.

                  I am thinking if the fan is already spinning at the slow speed, when it kicks up to high speed, there will be less strain resulting in less blown fuses like others have experienced. Does the low speed really not push enough air through the radiator to start cooling?

                  Also, 61311364272 is a 92* switch part number according to bav auto. This means that high speed will kick in after it would with the 80/88 switch.

                  Help me decide!

                  Comment


                    Low speed is sufficient in most applications, it just runs a little longer, which isnt necessarily a bad thing either. Some applications/climates require high speed to wash off all the heat. M42 radiator + Florida for instance

                    Check Us out on Facebook
                    Needing a harness adapter or wiring help? Check it out: also have 24v motor mounts, E30 M3 covers and E36 ECU mounts!
                    Full Product Line Tuning
                    OBD2 Tuning Available! OBD2 E36, S54 Swap, S62 Swap, etc: tuning@MarkertMotorWorks.com Dyno Thread

                    Comment


                      Originally posted by 328ijunkie View Post
                      Low speed is sufficient in most applications, it just runs a little longer, which isnt necessarily a bad thing either. Some applications/climates require high speed to wash off all the heat. M42 radiator + Florida for instance
                      Got ya. I am in new england but would like to be prepped for the worst since we have heavy traffic at random times. I have a brand new 325 radiator.

                      Comment


                        Hey all,

                        I recently purchased a 84' 325ES that had an electric fan and no clutch fan but the electric fan was wired always hot so the motor never got to the proper temperature.

                        I purchased the relay, wiring and switch listed in the OPs original post. The problem I am having is the switch never closes when the engine is up to temperature.


                        I installed the new sensor in the lower port on my radiator, it gets warm but not so hot you cannot touch. I do not think I have an air bubble in the system as the heat blows hot.

                        I am wondering if the sensor I bought is not the right one for my setup? maybe I need a lower temp one for the location on my rad? I have confirmed my wiring is correct by shorting across the temp switch and the fan comes on. Also when removing the top sensor no fluid came out of the rad but fluid did come out of the lower port when installing the new switch....



                        Thanks for any help!

                        Comment


                          need to try to bleed better. The ETA radiators can get airpockets trapped up by the sensors and then they dont work. Thats why they lowered the port down on later radiators.

                          Check Us out on Facebook
                          Needing a harness adapter or wiring help? Check it out: also have 24v motor mounts, E30 M3 covers and E36 ECU mounts!
                          Full Product Line Tuning
                          OBD2 Tuning Available! OBD2 E36, S54 Swap, S62 Swap, etc: tuning@MarkertMotorWorks.com Dyno Thread

                          Comment


                            Good write up!
                            - S50 Swapped E30 1/1 Mineral White -
                            @vaughnbannister on IG

                            Comment


                              Great write up

                              One of the things I need to take care of yet. Gotta make it. Great write up. Really should be a sticky

                              Comment


                                Wire diagram confused me.

                                I want to move the aux fan (low & high speed) to a circuit that is on whenever the ignition is on (sometimes my temp gauge climbs a bit high when I sit at a stop w/o A/C on).

                                I only recently found out that the fan is only available when the A/C is on, but even knowing that, I would rather have the circuit live when ignition is on, and controlled by the temp switch.

                                Looking at the wiring diagram, I saw a 30A fuse (#20) and a 7.5A fuse (#19) in the same circuit (?).

                                I'm trying to figure out where I should disconnect the supply which comes from the snowflake switch and splice in an IGN controlled power source (or control voltage, if the source for fan power comes from a relay, and the snowflake circuit just activates the system).

                                Comment

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