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Hot Rods Electric Fan Wiring Question?

Discussion in 'The Hokey Ass Message Board' started by johnod, Mar 23, 2018.

  1. johnod
    Joined: Aug 18, 2009
    Posts: 780

    johnod
    Member

    Hoping someone can shed some light on this.
    The electric fan in my car quit.
    I hooked it directly to the battery, to test and it works fine.
    Checking I find the fuse burnt and the fuse holder melted.
    Loose connections at the relay, so think that was the problem and will replace fuse holder.

    There is also a relay, and a adjustable temp controller.
    All this has worked since before I owned the car, ten years at least.

    Here's what has me confused.
    The hot goes to fuse, and then to 86 on relay.
    There is a jumper from 86 to 30.
    The two wires from the fan run directly to 85 and 87 on the relay.

    The adjustable temp controller, has two wires connected to it both go to separate grounds, and of course the sensor in the rad.

    I don't understand how this works at all, where's the fan ground, why are both wires from fan going to relay?

    I looked on line and find wiring diagrams and none of them look like that.

    Can someone shed some light on this, or have I got screwy wiring that somehow has worked for years?

    Thanks for any help.
     
  2. fordor
    Joined: Jan 27, 2007
    Posts: 36

    fordor
    Member
    from Finland

    This sounds wrong.
    I should do it like this. Relay 30 hot from fuse, 86 from temp controller, 87 to fan, and 85 to ground. And the fan second wire to ground. And check the turning direction on the fan.
    Peter
     
    lothiandon1940 likes this.
  3. johnod
    Joined: Aug 18, 2009
    Posts: 780

    johnod
    Member


    Thanks very much, that sounds much more like I figured it should be wired too.
    Is there a reason why you say check fan direction, can it turn backwards, and why would it?

    Thanks again.
     
  4. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,918

    sunbeam
    Member

    2 speed fan??? A DC fan will run backwards if polarity is reversed
     
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  5. johnod
    Joined: Aug 18, 2009
    Posts: 780

    johnod
    Member


    Ok got it, thanks. It's just a single speed fan.
     
  6. Hope this helps. relaywire[1].jpg
     
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  7. Sheep Dip
    Joined: Dec 29, 2010
    Posts: 1,572

    Sheep Dip
    Member
    from Central Ca

  8. johnod
    Joined: Aug 18, 2009
    Posts: 780

    johnod
    Member

  9. olscrounger
    Joined: Feb 23, 2008
    Posts: 3,901

    olscrounger
    ALLIANCE MEMBER

    looks right--it closes the relay by ground to fire the fan-wife's 55 fan wired like that for years with a manual switch and a trinary switch to run fan when ac is on
     
    Last edited: Mar 24, 2018
    lothiandon1940 likes this.
  10. I wouldn't wire it like that myself, but it will work that way. I've seen relays wired like that. I use term. #85 for ground and term. # 86 for Pos. for the relay coil.
     
  11. No. It's just like reply #7 only more detailed.
     
  12. Work In Progress
    Joined: Dec 14, 2010
    Posts: 154

    Work In Progress
    Member

    Is an adjustable thermostat really necessary? You could buy a fixed coolant switch for a few bucks that would ground the relay at a fixed temp and open at lower fixed temp. Many temperatures to choose from.
    Seriously though, how many time does one need to adjust their fan temps?


    Sent from my iPhone using The H.A.M.B. mobile app
     
  13. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    Member
    from Wisconsin

    They usually come as a kit so the variable temperature control is used so it can be set as needed. Where it is positioned in the system makes a difference in what the temperature setting needs to be.
     
  14. johnod
    Joined: Aug 18, 2009
    Posts: 780

    johnod
    Member

    Well we have success, just have to tidy a bit now, thanks everyone for all the information and help.

    John
     
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  15. johnod
    Joined: Aug 18, 2009
    Posts: 780

    johnod
    Member

    What temp do you guys set the fan to come on?
    I was thinking about 190?
     
  16. Petejoe
    Joined: Nov 27, 2002
    Posts: 10,511

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    Yes slightly above operating temperature.
    Generally Operational temps were at 180 for unpressurized systems and rose to 195 or higher for pressurized radiators.
     
  17. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,763

    Blues4U
    Member
    from So Cal

    olscrounger likes this.
  18. Should be set to come on about 30 degrees above thermostat opening temperature and off about 15 degrees above thermostat opening temperature.
    I use 180 degree stat. Fan goes on at 210 and off at 195. Works great.
    Fan almost never runs unless I'm stopped at light. Fan will lower coolant temp while standing still. Fan goes off when I get rolling.

    Sent from my LGL158VL using The H.A.M.B. mobile app
     
  19. johnod
    Joined: Aug 18, 2009
    Posts: 780

    johnod
    Member

    Alright , thanks again, will get it set once the snow is gone then.
     
  20. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 5,090

    Ebbsspeed
    ALLIANCE MEMBER

    #85 and #86 are interchangeable. The coil in the relay is isolated so it really doesn't matter which is positive and which is negative. It's a basic DC electromagnet so will work either way.
     
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  21. Mine comes on at 190, off at 170. So it never runs for long at all. It traffic it will run for maybe 2 or 3 minutes. My t-stat is 180. I used a Spal kit I got on eBay, came with a full install kit. Look around online for their instructions which are very good.
     
  22. In most cases that is correct. However, some relays have an internal diode to prevent voltage surges when shut off. More for use on vehicles with sensitive electronics on board. On these relays, which look the same from the outside and will plug in to the same socket, term # 85 is to be used as ground. Because all relays aren't created equal, I wire all my relays this way. As stated above, most circuits can be wired either way with no problem.
     
  23. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 5,090

    Ebbsspeed
    ALLIANCE MEMBER

    Thanks for that tidbit, never knew about the diode version. To further confuse the issue I discovered there are both positive and negative terminal #85 versions.

    https://www.delcity.net/store/Relays-with-Diode/p_73578.h_801565

    https://www.delcity.net/store/Relays-with-Diode/p_73578.h_73862
     
  24. buck 32
    Joined: Oct 16, 2014
    Posts: 181

    buck 32
    Member
    from Maryland

  25. I was unaware of that pos #85 term. relay. I guess that just means there is never an always or forever. :) Or never for that matter.
     

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