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  1. #1
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    Which thermo fan switch to run with a cooler 180f thermostat?

    Trying to get the smaller things out of the way. I think my fan as it is is always bouncing off and on every 10 seconds regardless of temp and stays on when it hits 210 on hotter days.

    I guess I'd want something that turns on at 200f and off at 190f? Not sure where to look, thanks.

  2. #2
    RallyJeep GO
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    A few questions: what intake manifold do you have? Any particular reason for running a 180* t-stat?

    Somewhere around 200* on, 195* off would be good for a 180* t-stat, IMO. 5* range keeps the fan cycles from being overly long and creating huge temperature swings.

    Be aware, the fan also runs based on A/C high side pressure, so that's likely the frequent cycling. If the weather is under 60 - 70* and you have the A/C on, the fan will cycle at idle. In warmer weather with A/C on, it'll just stay on when idling.
    1998 ZJ 5.9 Limited - Deep Slate
    Mods: Big trans cooler, 231 swap, Indy MA-X heads prepped by IMM, Comp 20-744-9 cam, 1.7 HS roller rockers, 52mm TB, Airgap manifold, DT headers and full 3" exhaust, SCT tune homebrewed by me, Martin Saine valve body, B&M tranny pan, magic suspension made from unicorn tears, power steering cooler, lots of lighting mods

  3. #3
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    I'm guessing your low speed fan isn't working, and is causing your problems. Low speed you would hardly know it's on, but it's enough to keep the high speed from kicking on in almost all situations - which is why the low speed windings always burn out first.
    I have a 180 thermo with stock temp switches and it works just fine. I know... I should have lower temp switches, but it just doesn't get that hot in Seattle to cause temp fluctuation.

  4. #4
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    4bbl m1 and 58mm TB waiting to be thrown on. Have shitty 91 California gas here so wanted some detonation protection. Plus it gets in the 100's during summer in the valley.

    I think my low speed is fine, I can only hear it with my window down at slow speeds. I don't think I've ever heard the high speed kick on, may not be working. Was triple digits last year, driving around town, AC on and the fan just stayed constantly on but I don't think it was louder than usual. Probably get a new fan to be safe. Love the weather in Seattle, I'm sick of sunshine haha.

  5. #5
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    You can test it by unplugging the upper temp switch and jumping the terminals with wire or paperclip, with the key turned to 'run'. It should spin. If it does the chances are extremely slim the high speed is out, but you can test it the same way on the lower switch wires.
    I'll trade you some rain for some sun, but you can keep your triple-digits!

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