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  1. #1
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    Default Radiator temp switch

    so I'm doing a cooling system mod using electric fans.
    I ordered an adjustable switch from summit to control the main fan (which will hit 2800 cfm) that will be controlled by a switch mounted in a '95 style water inlet that has the spot for a screw in sensor
    the secondary fan will be controlled by the sensor in the radiator ... '89s had the sensor on the driver side of the rad.
    its currently set to turn on at like 220 or when the AC is on.
    my question is this:
    a) I've removed the AC. Can I just go switch t relay? and cut the rest of the connection out?
    b) what temp is that switch set for? ~ will it open / close at temp?

    my plan is that the main fan will kick on at195 / off at 180
    and I'd like the secondary fan to kick on around 215 / 220 and off at 210 = is that stock?
    Last edited by Infidel Edition; 03-02-2014 at 08:30 PM.
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  2. #2
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    Default Re: radiator temp switch

    I'm not sure about the answers to a and b, but yes, auxiliary fan kicks on around 218 and back off around 210

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  3. #3
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    Default Re: radiator temp switch

    I believe the stock fan clutch fully engages at around 200F. What temp thermostat are you using?

  4. #4
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    Default Re: radiator temp switch

    The original auxiliary fan switch sends info to the pcm and down the line turns the fan on and off. Whether taking the computer out of the equation will cause problems, i don't know. But if it were me, for sake of easy installation and troubleshooting i would leave the factory setup and add a '91+ thermostat housing with the switch opening made in (in '91 they moved it from the radiator to t-stat housing) and just put a second switch in it for the other fan. If there's another way, i wouldnt be the best to know.

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    Last edited by XJ Wheeler; 03-03-2014 at 10:48 AM.

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    Default Re: radiator temp switch

    Quote Originally Posted by abebehrmann View Post
    I believe the stock fan clutch fully engages at around 200F. What temp thermostat are you using?
    I have the stick 190 thermostat and no real cooling issues
    ...but the plan is to remove the mech fan and run an electric that will kick off and on independent of the engine running


    Quote Originally Posted by XJ Wheeler View Post
    The original auxiliary fan switch sends info to the pcm and down the line turns the fan on and off. Whether taking the computer out of the equation will cause problems, i don't know. But if it were me, for sake of easy installation and troubleshooting i would leave the factory setup and add a '91+ thermostat housing with the switch opening made in (in '91 they moved it from the radiator to t-stat housing) and just put a second switch in it for the other fan. If there's another way, i wouldst be the best to know.

    Sent via messenger pigeon - i talk, he types.
    That's kind of what I was thinking... but maybe a slightly lower temp switch. ~ like 210 on...
    I ordered a '91+ housing and an adjustable switch that is the same thread.
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  6. #6
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    Default Re: Radiator temp switch

    The lower temp logic is that the cold side of the radiator at 218 isn't 218 at the housing.
    So by the time that sensor is 218 +/-, the housing is ???
    I generally only break 210 in crappy traffic...
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  7. #7
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    Default Re: Radiator temp switch

    I have electric fans. Mine come on at 200 at the tstat. I think that is the best. The Jeep system of turning it on at 205 at the cold side is way too warm for me
    230 hp 4.3L Chevy
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  8. #8
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    Default Re: Radiator temp switch

    Quote Originally Posted by 4.3LXJ View Post
    I have electric fans. Mine come on at 200 at the tstat. I think that is the best. The Jeep system of turning it on at 205 at the cold side is way too warm for me
    so you don't use the rad. thermostat?
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  9. #9
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    Default Re: Radiator temp switch

    My stat is mechanical and so is the temp switch/relay that operates the fans
    230 hp 4.3L Chevy
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  10. #10
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    Default Re: Radiator temp switch

    I have the thermal mechanical radiator switch (open under ## and closes at ## = turning the fan off/on)
    its located on the bottom 1/3, drivers side of the radiator...that controls the aux fan.
    I picked up a '91+ water housing so I can use a 2nd thermal switch for the main fan...
    I can stick a 190 on / 180 off switch there...

    what I trying to figure out is, the stock thermal switch in the radiator... can I simply put a lower temp switch ~ 190 = on? (which isnt190 at the water inlet housing)
    or would that create issues since its apparently tied to more than just the fan?

    my thought was to unplug it from ?? and replace with the lower temp switch and run that with the current replay.

    am I running in circles? = need more coffee...
    Last edited by Infidel Edition; 03-03-2014 at 10:25 PM.
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  11. #11
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    Default Re: Radiator temp switch

    Yes, you can do it. Just finding a switch though is tough. We found one, probably the last in existance for an early volvo I believe that turned on at 170 on the cold side. Worked well for a 195 stat. This was on Project HUM WEE, but it was not for a 4.0. Anyway it turned on the fans when the cold side was at that temp. I know Chrysler says these run hot, but I know Wranglers and ZJs run cooler so I think they just didn't want to fess up to a marginal radiator
    230 hp 4.3L Chevy
    Built 4L60E with manual lockout
    Atlas 4 speed
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    On board air
    Warn 9.5ti on custom bumper
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    30 gal gas tank
    lockers
    And a bunch of other stuff

  12. #12
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    Default Re: Radiator temp switch

    Quote Originally Posted by 4.3LXJ View Post
    Yes, you can do it. Just finding a switch though is tough. We found one, probably the last in existance for an early volvo I believe that turned on at 170 on the cold side. Worked well for a 195 stat. This was on Project HUM WEE, but it was not for a 4.0. Anyway it turned on the fans when the cold side was at that temp. I know Chrysler says these run hot, but I know Wranglers and ZJs run cooler so I think they just didn't want to fess up to a marginal radiator

    Those switches are a bit like the thermostat in the XJ .... Commonly used in a variety vehicles & a dime a dozen & available in quite a few temp configurations.

    RockAuto lists an Airtex Wells 1S4430 as the stock, aftermarket, thermo-fan switch for an 89 ... Airtex Wells, and other brands, have a bunch of different temp switches - of the same dimensions,

    ... Some are even capable of operating two fans - At different temps,

    Should be a 22mm thread with a 1.5mm pitch ... finding a connector to suit the preferred temp rating switch may be an issue tho ...

    ... but a sharp knife and duct tape is always handy .. ..

    When shopping ... just ask the parts store bunny for a look at a switch suppliers catalogue - instead of asking for a switch that fits an XJ.


    As for wiring the fan controllers ... I would leave the factory wiring alone and fit a, stand-alone, setup ... just like using a plug and play, aftermarket headlight harness ..

    Coz the temp switch is tied into so much on my 97 ... I'll be unplugging the aux fan and plugging the PCM side to a warning light/LED I will fit in the dash,

    I'm sure the dumb PCM will be just as happy turning on a light at 215 ... as what it is a fan ..

    .... Then with new relays and switch ... I will do whatever I want with the factory aux fan,
    ... and the poor little PCM - will be none the wiser ..


    Just in case its useful for working out fan start temps,
    ... The clutch fan should be engaged at about 170ish ... and disengaged at about 150ish ... according to factory specs for the air temps needed behind the rad .... Coolant temps will obviously be a little higher.
    Last edited by Carves; 03-04-2014 at 09:48 PM. Reason: stoopid bloody wifi tablets that need a toothpick to stab at the keyboard
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  13. #13
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    Default Re: Radiator temp switch

    Quote Originally Posted by Carves View Post
    Should be a 22mm thread with a 1.5mm pitch ...
    I thought the threads were 3/8 NPT
    ...is that just on the '91+ water inlet (the only spot I found thread reference for)?
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  14. #14
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    Default Re: Radiator temp switch

    No they are metric
    230 hp 4.3L Chevy
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  15. #15
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    Default Re: Radiator temp switch

    Quote Originally Posted by Infidel Edition View Post
    I thought the threads were 3/8 NPT
    ...is that just on the '91+ water inlet (the only spot I found thread reference for)?
    I was referring to what switch should fit in the big bunghole in the cold end of the Rad.

    I'm pretty sure the sensor thread in the t'stat housing is also metric as 4.3LXJ mentioned but I haven't measured one.
    I hate watching simplicity and reliability being ruined by bureaucracy and technology.

    Quote Originally Posted by MattybPDX
    If my jeep is going to be a grocery getter it's at least going to be a friggin awesome one.

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