Cooling Fan Switch And Temp Sensor Recommendations

[DirtySouthXJ]

Hi,

There is a (ebay/amazon) triple electric cooling fan system (semi) installed on my 96 XJ by the previous owner, but he wired it by tapping into a fuse in the PDC (no relay, fans turn on with key on). It looks like an adapter was added where the factory coolant temp sensor was, in order to add a second coolant temp sensor for an aftermarket coolant temp gauge; so currently there are two coolant temp sensors at that location.

Here is what I would like to do:

- End up with a properly wired and functioning fan system.

- Install the aftermarket coolant temp gauge. Currently all I have is the idiot light cluster.

Questions I have:

- Would there be any ill effects if I were to disconnect the factory temp sensor and install a coolant temp switch in it's place?

- Is there a port in the intake, head or block that I can install a coolant temp switch in to turn the cooling fans on, to avoid having to splice an inline adapter into the coolant hose?

If not..

- Can anyone recommend an inline adapter kit (preferably with temp switch, fan relay, wiring etc.)?

- Does anyone know the size of the coolant hose (I'm guessing i.d. to fit over adapter o.d. ? )


Regardless of temp switch installation location..

- I see different coolant temp switch on/off temp specs (on 200°/off 185° etc.), what spec switch should I use in this application (96 XJ 4.0)?

Thank you!

 

[RCP Phx]

Don't mess with the factory sensors as they report directly to the PCM. Most systems of that type mount their temp sensors on the radiator itself and control the fans in stages.

 

[RCP Phx]

As for the separate temp gauge, pick up a t-stat housing with the extra tapped port.

 

[DirtySouthXJ]

Don't mess with the factory sensors as they report directly to the PCM. Most systems of that type mount their temp sensors on the radiator itself and control the fans in stages.

That's what I was thinking, that the factory sensor is for more than just factory temp gauge/cooling fan activation. The radiator is also aftermarket (aluminum), I'll see if there is a threaded port I can mount the aftermarket switch to.

As for the separate temp gauge, pick up a t-stat housing with the extra tapped port.

There is already two units there, the factory temp sensor and the aftermarket gauge temp sensor. I need a third port for the electric fan temp switch. I know small block Chevys have multiple ports in the intake manifold/head/block, I'm wondering if the Jeep 4.0 has similar. I could add a spliced in adapter to the coolant hose but would like to avoid that if possible.

Do you have any idea on what cut on/cut off specs I should be looking for on the fan temp switch? For example 200° fan turns on, 185° fan turns off? I saw a similar triple fan system supposedly for an XJ and it comes with a 180° on 165° off temp switch. Not sure what temp range I need.

 

[RCP Phx]

That's why electric systems monitor the radiator outlet temps, the t-stat controls the engine temp. They typically turn a fan on at about 160-180 and add fans if the outlet temp continues to rise.

 

[DirtySouthXJ]

That's why electric systems monitor the radiator outlet temps, the t-stat controls the engine temp. They typically turn a fan on at about 160-180 and add fans if the outlet temp continues to rise.

Copy, thank you brother! So it sounds like the 180° on 165° off temp switch would work well. I noticed that when powered, two of the three fans come on (with no temp input, fans are hardwired direct to key on power currently). I'm guessing the third is for situations you describe. This is all new to me; I'm used to large single, center mounted, mechanical fans on GM vehicles. If there was a way to swap over to a setup like that on the 4.0 in a XJ, I would.

 

[DirtySouthXJ]

Alright, so doing some more digging..there are supposedly two coolant temp ports on some 4.0 XJ's (evidently depends on year, mine is a 96). One is at the thermostat housing and is the coolant temp sensor used by the PCM for data to control the engine; the other is at the back of the head on the drivers side and is the coolant temp sender for the gauge. I'll have to see if this port (at the head) is present; because if it is, then I won't need any additional adapters etc. to add a third sensor/sender to switch the aftermarket fans on.

Does anyone know the thread size/pitch for the ports at the thermostat housing and at the head?

 

[Unclewolverine]

The one at the back of the head is extremely small. You probably won't be able to use it for any aftermarket parts.