• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Aux fan wont kick on.

GrimmJeeper

NAXJA Forum User
Location
Gardena, CA
87 Renix manche, 4.0

i cant get the aux fan to kick on. on my HO 95 if i turn the AC on or unplug the temp sensor, the aux fan will start right up. niether of these methods work on my MJ, the aux fan will not turn on at all :dunno: it isn't overheating or anything, i just want to be sure everything is working as it should be.

im not familiar with the renix systems, is this normal?
 
Does the a/c work on the Manche? On my 94 when the A/C was shot the aux fan never turned on.

Unplug the fan from the wiring harness and jump it directly to the battery to see if that will turn it on, if it does you've eliminated the fan motor from the equation.
 
control circuit ground for fan relay runs through AC clutch when AC is on. If the AC clutch has an open winding, the fan relay isn't grounded and neither the fan nor the AC will work with AC switch. As for no fan with high temp AND no fan with AC, I'm not sure where the ground for the temp switch (in radiator) actually is attached, but I'd find it hard to believe both grounds just happen to be bad. Pull the fan relay and jump the fan power circuit and make sure the fan turns and then use a 9V battery on the control circuit pins on the relay to make sure it works (#85 & #86)

I'm assuming that as a parts guy, you know how to check a relay, but if not lemme know-- I'm just too lazy to type it unless it's necessary
 
the relay is fine, the fan motor is fine. those were the first two things i checked.

im thinking the ac might be the problem. the wire going to the compressor clutch is disconnected, and it has some hack job ac compressor in it with an 8 rib pulley.. its a huge Sanden compressor. it looks like a butchered r134 coversion, the hoses are routed all over the place it looks terrible. it doesnt overheat, it actually runs very cool since we changed the waterpump and tstat this weekend, so im not sure if high temps would kick it on. i just assumed that unplugging the temp sender would turn it on as sort of a failsafe like my later model XJ does.

do the renix models work the same way, turning on the fan when you unplug the temp sensor?

thanks for the replies guys :cheers:
 
no-- temp switch actually grounds the control circuit for the relay (IIRC) and turns fan on. You should be able to jumper wire the plug for the temp switch in the radiator and have a fan.

All of this is from memory two years ago, and I could be wrong..... but that's never happened before..
 
I had removed the AC stuff except the compressor on my 89 XJ and the aux fan would no longer come on. There is a round 2 prong plug that I think plugged into the area around the dryer. Once I jumpered the contacts in the plug the fan now comes on with the AC switch. Even with the compressor disconnected.
 
I had removed the AC stuff except the compressor on my 89 XJ and the aux fan would no longer come on. There is a round 2 prong plug that I think plugged into the area around the dryer. Once I jumpered the contacts in the plug the fan now comes on with the AC switch. Even with the compressor disconnected.

that would be the low side pressure switch. It needs to be jumpered and the circuit needs to run to a ground to control fan with AC switch.
 
big fat two wire sensor on drivers side tank
I don't have this sensor. there is the upper and lower connections for the internal trans cooler, which are capped off because i have a 5 speed, and the connection for the lower radiator hose.
 
still got an '87 motor? Where's the CTS that you're unplugging located?

everything I've got sez it should be above lower radiator hose and below the top trans. cooler line. It's a screw-in sensor with a couple inches of pigtail and a two wire plug. Was this possibly a newer radiator from something that had the CTS in the water outlet?
 
Last edited:
still got an '87 motor? Where's the CTS that you're unplugging located?
as far as i know its original. the radiator looks like its been replaced recently, but i just bought the MJ so i dont know the history of it.

the sensor i am unplugging is at the back of the head on the drivers side.
 
there is a 2 wire connector not plugged into anything down near the front of the airbox, leading to a relay on the inner fender well. could that possibly be the connector you are talking about?

small one wire unit?

yes.
 
the one wire sending unit...

all that does is tell the temp gauge how warm you are. There should also be one in the drivers side of the block to tell the onboard computer the coolant temp (true CTS) and a fan switch in the radiator as well. Look for a two wire female plug next to the plug for the fan itself. IIRC, it's in the same bundle. I'll go out and verify in a couple seconds....


yup... for honest and for true, it's really there! Big fat S.O.B. directly under the top trans. cooler line with two wires out to a plug. I'd give you some wire colors, but the two on the switch are wrapped in a cover, and I've relocated my horn directly over the harness. The plug should be right next to the little orange diode-looking plastic thing immediately in front of the air box.
 
Last edited:
i'll look at it again tomorrow Shorty, thanks for the help. maybe i'll snap a pic so you can see the plug im talking about.

:cheers:
 
Back
Top