Radiator temp switch

[Infidel Edition]

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?

[Brasscatz]

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

Sent from my Samsung Galaxy S4 because my microwave couldn't do it

[abebehrmann]

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

[XJ Wheeler]

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. ;)

Sent via messenger pigeon - i talk, he types.

[Infidel Edition]

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



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.

[Infidel Edition]

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...

[4.3LXJ]

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

[Infidel Edition]

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?

[4.3LXJ]

My stat is mechanical and so is the temp switch/relay that operates the fans

[Infidel Edition]

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.

:morningcoffee: am I running in circles? = need more coffee...

[4.3LXJ]

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

[Carves]

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 .. :rolleye0012: .. :D:D

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 ..:D

.... 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 .. :D


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.

[Infidel Edition]

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)?

[4.3LXJ]

No they are metric

[Carves]

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.

[Infidel Edition]

So I ordered (as usual~before posting = measure with a micrometer, mark with chalk, cut with a chain saw...)
But the luck of the Irish be with me + I remembered seeing a thread on this....
And had ordered last week.
Parts started coming in and
4740
3/8 NPT works on the '91+ water neck.

Gonna hold off on the radiator for now... maybe order a stock replacement switch to run the aux