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Thread: fan relay gets hot

  1. #1
    The Texan TexCJ7's Avatar
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    Default fan relay gets hot

    i wired up my electric fan using a 20amp relay and it is ground activated by a toggle switch right now i only turn it on when i stop because while driving engine temp stays around 200 with the fan off but there is no way i can go on the trail as is

    is a 20 too small what size do i need so i can leave it on without it burning up
    2012 kawasaki Teryx4

    Sold-85 CJ7, 6 inch lift, siting on 36's, welded rear, lots of drain holes

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    Quote Originally Posted by TexCJ7 View Post
    it is ground activated by a toggle switch
    If I understand correctly (which would suprise me), you have the pos + (technically neg - ) wire going from the toggle to the relay, then from the relay (I think # 30 on relay) ground - to activate the relay?? Sounds correct to me. How many amps is needed to start/ then operate the fan? That should dictate relay size. What size fuze do you have installed (before) the switch/toggle?

    What most of us CJers have a problem with is grounding issues. Have you run a battery to frame, tub to frame, dash to tub ground wires. Typically in the #0 to 2, #2 to 4, #10 gauge wires respectively.

    JeepHammer on Jeep forum has mentioned many problems with AMC's saving on wiring (to small - ie #20 gauge instead of #16/14 gauge - which creates heat), and not enough ground-wiring. Maybe something to look into adding.

    Later, T.J.

  3. #3
    darwinism at its best irish1371's Avatar
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    wire size could be an issue. I am surprised that you do not use a 30 amp relay, but if the 20 is working then it must be ok. Is the fan 1 or 2 spd? your fan may be right on low spd but too much for your setup on hi spd?
    "Some people wonder their whole lives if they will ever make a difference. Marines don't have that problem." Pres. Ronald Reagan
    Army vs Marines = http://www.youtube.com/watch?v=_2M7ckkxQLU

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    The Texan TexCJ7's Avatar
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    i have no idea what fan it is, it was in it when i bought it, today i put a 40amp on it and put a 40 amp fuse from the battery to the relay it seems to be doing better it still gets warm but not as hot as the 20

    the way i have it grounded is from the 30 to a toggle switch and the from the toggle switch to a screw under the dash
    2012 kawasaki Teryx4

    Sold-85 CJ7, 6 inch lift, siting on 36's, welded rear, lots of drain holes

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    darwinism at its best irish1371's Avatar
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    I bet the "a screw under the dash" is your heat problem. If you look there should be a common ground stud under there, try moving to the common
    "Some people wonder their whole lives if they will ever make a difference. Marines don't have that problem." Pres. Ronald Reagan
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    Quote Originally Posted by irish1371 View Post
    I bet the "a screw under the dash" is your heat problem. If you look there should be a common ground stud under there, try moving to the common
    You could add a 10 gauge (minimum) wire back up to the battery from the 'screw under the dash', just one more link to better grounding.

    Later, T.J.

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    Member warthog_cj7's Avatar
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    Why are you using 30 to a toggle switch? If using 30 on the ground side that should go straight to ground and 87 out the other side to the fan. 30/87 both should be 10ga. as these are your primary current carriers. 86 should be your toggle into the relay and in this case 85 to positive. 86/85 can be 18ga. as they are only being used to trip the relay.

    Sounds kinda like someone hooked it up as a big fuse.

    Normal relay setup for fan is 30 to fuse to +12v(10ga), 85 to fan or fan thermo controller on the + side(10ga, Neg of fan to ground 10ga too), 85 to ground(18ga), 86 to toggle(18ga to acc pwr).

    If after that, if the relay continues to get hot, sounds like the relay is on the way out and pullin more amps than the circuit is built for.
    Dan M.

    '85 CJ-7, 4.0L,T18,4.10s,35s,Fully locked,winch,cage

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