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Electric Fan not working

K

Khary23

NAXJA Forum User
Location
Brooklyn, NY and Worcester, MA
I have been having problems with my electric fan for the past several weeks. I have changed the relay as well as the coolant temperature sensor, but it is still not working properly. It will come on when I turn the A/C on, but stop working a few minuets later. It will also not come on when the temp goes over 220 degs. Is there a way to test if the problem is the fan it self or another component of the system?
Thanks in advance

Jeep info

1999 XJ
4.25"/4.5" lift, 31" tires no engine mods
 
Find which wire is positive and which is negative. run wire from each to the battery. one to pos and one to neg battery terminals.
 
I had a similar problem with mine. Turned out that it wouldn't work right if the refrigerant for the AC was too low for some odd reason.

Jeff
 
If you disconnect the temp sensor (by the thermostat housing) while the engine is running, the fan should kick on after a second or two...and it should stay on until you plug the temp sensor back or turn off the engine.

This should test the ECM, relay, wiring and fan.

But be warned, if you disconnect the temp sensor while the engine is running, the ECM should sense this as a fault with the temperature sensor, throw a code and you check engine light should illuminate.

Also, from 97 up...the electric fan does not automatically come on when the AC is turned on...it is all computer controlled and only comes on depending on temperature, pressure and status of the AC refridgerant (sp??). There was an article posted about it here a while back.

http://www.askamechanic.info/askamech2/content/view/73/47/

On my 2000, the electric fan only comes on when the AC is turned on if it is really hot outside and vehicle is sitting still, but most of the time, it only comes on if the coolant temperature gets close to 220F or so.
 
Last edited:
Thanks for the replys.

I disconnected the temp sensor as thebrick suggested and the fan kicked on after a second. Does this mean that the fan is good? And if so what else could be the problem? I don't think its the A/C refrigerant since it was filled last year.
 
That means the fan, relay, and ECU are all good, along with the associated wiring. Does the temp gauge read normal values when driving? If it does I think there probably isn't anything wrong with your jeep.

EDIT: It might be the fan I guess, dying after a certain amount of time turned on, try probing the fan connector with a test light and see if the light turns on but the fan doesn't.
 
The temp gauge will read normal temps and then after a while spike up to the red zone. It happens when in traffic with the A/C on, or driving in the city with the A/C on both low speed situations where there is not a lot of air flowing over the radiator.
 
Does the fan turn on when you use the defrost setting? If not then I would think it is the low pressure sensor. I don't use the a/c so I just jumped the switch so I could turn the fan on with the defrost setting. I would check your fan clutch as well. I ended up replacing mine with a HD fan clutch from a ZJ and it has made a huge difference. I thought my old fan clutch was fine but when I pulled it off I could finally see where it had been leaking. Easy check for the fan clutch. drive your rig around to get it all warmed up. Once it is good and warmed up pull over and pop the hood. shut it off and watch the fan. If it keeps spinning after you shut it down for a few seconds then it is bad. with your jeep all warmed up in the end of june in NY it should stop spinning almost immediately.
 
take a piece of wire and jump the ac low pressure switch. turn on the ac or defrost. If e-fan works then either you need to recharge your ac or the switch is bad. the fan clutch is installed on the mechanical fan. check that one for spinning after the jeep has been shut down.
 
Harness that plugs into it. You should be able to just jam a bent paperclip or something into the two wire sockets.

Both pressure switches are placed in series, so you may need to jump both. One is on top of the dryer up near the leak detection pump (rear passenger corner of the engine compartment) and the other is on the underside of a refrigerant line just behind the compressor.
 
take a look at this thread:

The sensor from NAPA was out of range causing the PCM not to engage the electric fan.




It also sounds like you may have a failing electrical connection somewhere in the fan power supply, or ground.

A poor connecting terminal may break contact after the fan starts and when terminal gets hot, opens the circuit.

A failing fan motor will do the same thing.

I wouldn't bother with the pressure switches in the A/C system as they have no effect on the fan directly. They merely let the PCM know the pressures are not too high or too low in the system to engage the A/C clutch. If the PCM turns on the A/C clutch, it should be turning on the fan too.
If the A/C clutch is on and the fan is not, there is a problem in the Fan circuitry, not the A/C.
 
Last edited:
Finnally had time to jump the pressure switch today and the fan turned on when I turned on the A/C.

Digger,
I think you maybe on to something as I have noticed that the problem only happens on hot days, or extended driving.
 
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