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    Results 1 to 8 of 8
    1. #1
      Join Date
      Oct 2004
      Posts
      2,544
      Country Flag: United States

      Wrong MarkVIII Fan - Now what?

      So I had picked up a MarkVIII fan out of the local yard some time ago (I think it was a 1998), along with a Volvo relay setup. Finally got around to install it (ordered a new BMW sensor that operates at two temperatures).

      It only seemed to operate on high when I temporarily connected it. Come to find out, i have the "single speed" version. It has the white harness connection, and the inspection cover. Removed the inspection cover to see the middle was just a dummy wire.

      My understanding is the factory system is pulse width modulated by the ECM to vary the speed. I'm not running an ECU. So should I just hook up the fan to run on the low end of the BMW sensor temperature? Is there a pwm controller that I should run instead of the Volvo relay/BMW combo?

      I also found this: https://www.summitracing.com/parts/f...yABEgIrbPD_BwE which looks to be an earlier model application, so it may be a two speed motor, but I can't be sure. I also have no idea if they are any good.



      My hope was to do this on the cheap. I'm not too electrical savvy, so please type slow. :-)
      Red Forman: "The Mustang's front end is problematic; get yourself a Firebird."


    2. #2
      Join Date
      Nov 2006
      Location
      Mountain Springs, Texas
      Posts
      4,488
      Country Flag: United States
      I just installed a pwm controller from DCC but will be a while before I can report back on how well it works.

      http://www.dccontrol.com/constant_te...ontrollers.htm

      Don
      1969 Camaro - LSA 6L90E AME sub/IRS
      1957 Buick Estate Wagon
      1959 El Camino - Ironworks frame
      1956 Cameo - full C5 suspension/drivetrain
      1959 Apache Fleetside

    3. #3
      Join Date
      May 2011
      Location
      Chippewa Falls, WI
      Posts
      290
      Country Flag: United States
      The mark 8 pulls a bunch of amperage on start up. I run mine off a 80A relay and large wires(10 gauge works but is IMO marginal, 8 gauge is better). Low speed runs off the ecu input for fan on, and high speed is wired to a switch that I can trigger manually. If I have a fuse or other issues on one circuit, i can use the other as a backup. It would be nice to be pwm'ed but the cost has not been justified yet for myself. My fan was also from a JY. so with the fan/wiring, I am into it for ~60-75 bucks total.
      Justin N.

      1966 Chevelle
      1992 GMC Typhoon
      1989 Jeep Wrangler CJ 6.0 Twin Turbo
      1981 Jeep CJ7

    4. #4
      Join Date
      Sep 2013
      Location
      Houston, TX
      Posts
      246
      Country Flag: United States

      AutoCool PWM Fan Controller

      A pwm fan controller will reduce the large inrush current when the fan first comes on. I have a Derale shroud with dual 13" Spal fans; the starting current for only 1 fan is about 25 amps, but the steady-state current at full speed is only 12 amps. A fan controller will ramp-up the fan speed gradually which eliminates the inrush current spike and takes a huge strain off the electrical system.

      There is another alternative to the OEM parts and the DCC controller mentioned in the previous post. A guy named Daryl builds a series of fan controllers called AutoCool - see pic below. The 50 amp unit sells for $139. I'm planning to run one of these fan controllers for my 72 Olds 442 convertible project. Hope this helps.

      Rodney

      Name:  AutoCool50.jpg
Views: 329
Size:  60.2 KB
      Rodney Meyers
      72 Olds 442 Rest-mod clone

    5. #5
      Join Date
      Aug 2004
      Location
      Harriman, Tennessee
      Posts
      1,288
      Country Flag: United States
      So far as I can tell, all the replacement motors are single speed. As others have stated, a fan speed controller is the way to go. If, on the other hand, you do find a two speed replacement motor, please let me know where you got it!
      Why do termites eat houses?

      Because they have
      Munchausen Syndrome.

    6. #6
      Join Date
      Feb 2009
      Location
      muggy midwest
      Posts
      533
      Country Flag: United States
      All Mark VIIIs are single speed fans. PM me for a robust 3-speed conversion harness-no need for a pwm controller with my design.
      "...if at first you don't succeed, try again.
      If you still don't succeed, then quit-no sense being a damn fool about it..."
      -W.C. Fields

      HARNESSWORX
      (formerly gmachinz)

    7. #7
      Join Date
      Feb 2009
      Location
      muggy midwest
      Posts
      533
      Country Flag: United States
      Here’s one of my resistor 3-speed harnesses powering a dual 14” HD fan assembly rated at 6,000 CFM. The fans running in parallel off my harness pulls 13, 23 and 32 amps on low, medium and high speed respectively. This assembly can be triggered off any PCM, GM temp switches or the BMW dual temp switch. No need for temperamental fan controllers-this is a proven circuit design!
      Attached Images Attached Images  
      "...if at first you don't succeed, try again.
      If you still don't succeed, then quit-no sense being a damn fool about it..."
      -W.C. Fields

      HARNESSWORX
      (formerly gmachinz)

    8. #8
      Join Date
      Feb 2009
      Location
      muggy midwest
      Posts
      533
      Country Flag: United States
      Any feedback on how everyone is doing with their Mark VIII fan controllers? I’m curious as to how well the latest generation of “revised/updated/improved” controllers are holding up.
      "...if at first you don't succeed, try again.
      If you still don't succeed, then quit-no sense being a damn fool about it..."
      -W.C. Fields

      HARNESSWORX
      (formerly gmachinz)





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