Budget Dual Fan Controller Setup / Taurus Fan Setup

Discussion in 'Electrical Systems' started by Aceshigh, Nov 20, 2010.

  1. Fbird

    Fbird Veteran Member Lifetime Gold Member

    3,053
    329
    Feb 12, 2011
    atlanta, ga
    sound like your bmw switch is NOT isolated from ground AND OR your LED's should ONLY have SWITCHED power to them.
    The volvo controller--- to ---- bmw switch ----- to bosch relay ---- is path for GROUND. The volvo control is input hot #30 and 2 output hots for FAN. The thermal switch is ONLY breaking the GROUND connection.
     
  2. junkyardZ28find

    junkyardZ28find Veteran Member

    771
    7
    Mar 4, 2012
    des moines, iowa
    I've been building a lot of electric fan as well as reproduction replacement harnesses and I am not a fan of using a relay to provide a switched source to ground path. The way the BMW dual temp switch works is by engine grounding the center (T3) lead, then T1 goes to low temp Volvo ground trigger 1 and T2 goes to Volvo ground trigger 2. If I were you Nacho, re-wire the ground circuit and use that relay instead to provide a +12V switched power source via #30 to the Volvo relay input from #87. Also, Id suggest grounding your LED's to chassis and then tap them into your Volvo 1 and 2 outputs so they illuminate whenever either speed is activated-since all power to the Volvo relay is killed via your re-wired control relay when you turn the key off, this should get rid of your LED power draw.
     
  3. nachomax

    nachomax New Member

    3
    0
    Jul 27, 2013
    Los Angeles, CA
    Hi Fbird,

    I should have clarified that once the fan would go on low speed, the LED indicator for low speed would turn off, and leave the one that is for the high speed.

    I think this is what you mean volvo_relay_diagram.PNG

    I'll rewire my Bosch relay this way to get rid of the power draw like you said. Thank you!
     
  4. junkyardZ28find

    junkyardZ28find Veteran Member

    771
    7
    Mar 4, 2012
    des moines, iowa
    There you go-that should work perfect!
     
  5. clay's70

    clay's70 Moderator Staff Member Lifetime Gold Member

    That will work, i just don't like running the fan supply through a weaker bosch relay.
     
  6. junkyardZ28find

    junkyardZ28find Veteran Member

    771
    7
    Mar 4, 2012
    des moines, iowa
    I use commercial grade TYCO 40 and 60A relays for most fan setups and 75/100A TYCO relays for extreme duty fan setups like my F150 dual 14" fan setups and my 2008-up Mustang GT fan setups-but my kits differ in that they are conversion harnesses for 3 speeds.
     
  7. Fermentedwaste

    Fermentedwaste New Member

    1
    0
    Nov 27, 2018
    I know this is a super old but great writeup, does anyone know what or how i can wire in a switch to kick the fan on high when i turn the ac on? rather it not be a manual toggle switch but an automatic. Trying to work this out for my 1987 c10.
     
  8. ULTM8Z

    ULTM8Z Veteran Member

    8,764
    193
    May 19, 2000
    Los Angeles
    You could use the 12V A/C clutch trigger wire; branch off of that to also use as the 12V trigger for a relay controlling the high speed. The only thing is, the fan will then be on even when driving at speed when you don't need it.

    Computer controlled cars have the advantage of having the fans also controlled by the vehicle speed (i.e., fans off above 35 mph, say).
     
  9. junkyardZ28find

    junkyardZ28find Veteran Member

    771
    7
    Mar 4, 2012
    des moines, iowa
    If you’re really inclined, install a trinary switch to work off of AC liquid line pressure instead as an override...that’s the closest you’ll get to an automatic setup for AC override w/o having computer controls.
     

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