Aux fan install on non-A/C equipped models.

[Dickinson County Comanche]

Hello all, I was wondering what it would take to install a factory aux electrical fan on my non-A/C equipped Comanche. Are all the wires there for the install? I know I’ll need a temp. switch for the fan to kick on, and the fan itself, but I was curious if I need to find that piece of harness to make it all work. 
 

Thanks!

-DCC

[jdog]

the wires are not there, they are a seperate a/c harness. you can make a harness, just be sure to put a relay and a fuse in it

[AZJeff]

I am not familiar with the cooling fan wiring on the older XJ/MJ series.  From what I can determine looking at wiring diagrams, the ECU controls power to the electric cooling fan motor via fan clutch relay.

 

I am assuming that the ECU uses the engine temperature sensor (and the heater control switch set to "A/C") to turn the fan relay on/off.

 

If one is going to add in an electric cooling fan option without the A/C, the trick will be to find a way to sense engine temperature and power up the fan outside the normal ECU control method, since I don't think you can tap into that practically.

 

I did this on an old F-150 truck by adding in a temperature switch into the upper radiator hose.  When the coolant got hot enough, the switch closed, and that turned on the relay that powered the fan.

[DesertRat1991]

This is a plug & play installation on the 91+ trucks.  All connectors are present in the harness and no extra sensors required.  Without A/C, the aux fan activates around 230deg and shuts off at 210deg.

 

IMO, these trucks should have never left the factory without an aux fan.

[jdog]

43 minutes ago, DesertRat1991 said:

hese trucks should have never left the factory without an aux fan.

I agree with that one, i will be sitting in the drive thru awaiting food and truck will start to get hot.

To install a fan and sensor is possible, just depends if you can find the a/c harness or if you just want to make one up.

[AZJeff]

On 2/12/2021 at 4:33 PM, DesertRat1991 said:

This is a plug & play installation on the 91+ trucks.  All connectors are present in the harness and no extra sensors required.  Without A/C, the aux fan activates around 230deg and shuts off at 210deg.

 

IMO, these trucks should have never left the factory without an aux fan.

I totally agree that all MJ/XJ vehicles should have had an electric fan, regardless of whether A/C was present.

 

that said, the OP’s truck is an 89, so his installation won’t be plug and play.  He will have to devise a setup like I described, using a temp sensor independent of the one used by the ECU.