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Hot Rods Electric fan switches

Discussion in 'The Hokey Ass Message Board' started by Fourdy, Feb 12, 2020.

  1. Fourdy
    Joined: Dec 9, 2001
    Posts: 454

    Fourdy
    Member

    I have a new vortec, roller cam/rockers sbc with a new 3 core aluminum radiator. I purchased the SPAL switch that says it turns on at 195 and off at 175. Question for you with much more experience with SBC's, would the fan run all the time because the engine normally runs more that 175? What do you use?

    Thank you so much,

    Fourdy
     
  2. olscrounger
    Joined: Feb 23, 2008
    Posts: 4,341

    olscrounger
    ALLIANCE MEMBER

    Have the same sensor in a mild 350--it cycles on and off. Has manual overide switch and also trinary switch from ac.
     
    porknbeaner, i.rant and Gman0046 like this.
  3. Gman0046
    Joined: Jul 24, 2005
    Posts: 6,260

    Gman0046
    Member

    Fourdy, your fan will only turn on when the engine temperature exceeds 195 degrees and will off at 175. Like olsrounger says the fan will cycle. You have no problem.
     
    Last edited: Feb 12, 2020
  4. Fourdy
    Joined: Dec 9, 2001
    Posts: 454

    Fourdy
    Member

    Wondering if your cars run normally at or below 175 so the fan is off for some time or runs most of the time because they run just over 175. I have been warned by some that SBC's like to run at about 180 +/-. Thanks for hanging in with me.
     

  5. I use the OEM switches that come on newer cars. A brass slug that screws into a 3/8" NPT collar that I solder into the bottom radiator tank. I like them 'cause they are simple and compact and I have a fighting chance of getting a replacement somewhere down the road. I don't pay much attention to the ratings, they are all within spitting distance of each other and as you say, will be on when the engine is running which is a good thing. This signals a common Bosch DPDT relay which powers the fan. Cheap, reliable, and replaceable.

    s-l1600.jpg
     
  6. When the fan comes on the temp drops. I got a 400+ HP SBC that even with a 195 T stat normally runs below 180 and often on the highway does not reach above 165. granted that is radiator driven a small rad may produce higher operation temps. LOL
     
  7. woodiewagon46
    Joined: Mar 14, 2013
    Posts: 1,916

    woodiewagon46
    Member
    from New York

    I am using the Spal set up and mine cycles on and off as needed. Driving along at 70 MPH it cools the car enough so the fan is off. Stop and go traffic the fan is on.
     
  8. My 355 is around 425 HP and runs 175-180 unless I'm stuck in traffic for a long time. I have a 16" Spal fan that comes on at 195, off at 175. It only comes on when I reach 195 and keeps the car cool from there. If I run errands, I come out and it may come on with the heat soak from sitting for a short while.
     
    olscrounger likes this.
  9. Fourdy
    Joined: Dec 9, 2001
    Posts: 454

    Fourdy
    Member

    Thanks to all for your comments and help. I'm anxious to get this 405 horse Blueprint Engine with 200-r4 on the road.
    Fourdy
     

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