smallclone

1995 cherokee sport, 4.0

ok so whats the deal with the aux fans on these jeeps.

replaced, coolant temp sensor, replaced fan relay. replaced water pump, replaced thermostat, checked the system for air. car runs at like 230 and fans will not kick on.

fans will work however if i turn on the AC but it will only stay on for about 45 seconds then turn off. or, if i unplug the coolant temp sensor the fan will kick on.

a little history on when this started.

i brought the car in to have the spark plugs replaced and while they were in there i told them to flush the system, got the car back and it started overheating, at this time the waterpump was making a terrible noise so i figured it was a no brainer and replaced that. after the sensor, relay, and thermostat, im at a complete loss here.

any suggestions?

AutobotXJ

Try replacing the relay with a known good one.

smallclone

Thanks but didnt you read the part of my post where i said i already replaced that.

AutobotXJ

Yeah, obviously i did. It still sounds like a bad relay or connection to the relay. Does the fan turn on if you jump it straight to a power source?

mcguyver_xj

When you unplug the temp sensor thats an automatic default setting set by ecm cause it doesn't know the temp honestly chrysler systems have lots of problems with fan relays but in a worst case scenario it could be a problem with the ecm

mcguyver_xj

Ohh also it seems your strictly relying on your aux fan to cool the jeep the aux fun is only in high heat situations you should really worry about the underlying problem my jeep with new t stat rad. And water pump never gets close to 200 deg. Under normal driving conditions

freegdr

if the ac compressor is cycling on and off so will the fan....

freegdr

as for the overheating issue hows the fan clutch?

smallclone

I have not tried to flush the system yet so thats next. The fan relay is good because you can switch it for the fuel pump relay and it works there.

As for the fan clutch, im not excatly sure how to check that for malfunctions?

I dont excatly want the aux fan as a whole to cool off the system but it just seems odd to me that they wont turn on and the car seems to like to rin at 225\235 degrees now.

I think though, if im going downhill or making a sharp turn the temp will spike for a second. I did check levels and bleed for air though.

johnydoe

i was told the reason my aux fan dont work is because it only turns when the a/c is on, he suggested that i plug the fan directly to the battery with a relay switch in the jeep so i can turn it on/off at will...plan to do it soon

413maxwedge

Info for the newbie's or those that don't know, 2000-01 electric fan will only come on at 218 degree's, 1999 and earlier electric fan comes on with a/c or at 218 degree's if a/c is off. Now on 2000-01 you can go to the dealer and have them flash the ecu or whatever you wish to call it (computer) so the fan will come on with the a/c also. Smallclone check your temp gauge with a mechanical gauge don't trust those factory one's and it sure points to a relay or a wiring problem I think.

mcguyver_xj

if the mechanical fan spins easy with almost no resistance its bad or if its wet around where it meets its shaft or if when you rev up it sounds like a jet engine even when cold

smallclone

Thanks for all the great info, the fan clutch was cheap so i will replace that tonight as well as flushing the system. If that dosent work i am clueless here.

smallclone

ok, SOME progress here,

i flushed the system and ran some cleaner through it and replaced the fan clutch.

car does run cooler now, about 215 ish, can spike to about 218 220ish.

drove it for a half hour, aux fan never came on once.

turned on the heat and it kicked right on.

now im stumped.

freegdr

thats what it is supposed to do ,running temp is normal ...drive it