2002 WJ fan not turning on - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > WJ Grand Cherokee Forum > 2002 WJ fan not turning on

Stainless Steel Door Hinge PinsPoly Door Hinge BushingsDual Color LED Light Bars White/Amber

Reply
Unread 05-03-2013, 12:30 AM   #1
CMARJEEP
Registered User
2001 WJ 
 
Join Date: Aug 2007
Location: Sacramento, CA
Posts: 2,672
2002 WJ fan not turning on

Hey guys. My cousins WJ 4.0l has been intermittently overheating lately. Only at idle. We narrowed it down to the fan not turning on. It only has the e fan. I replaced the fan relay as that seems to be the most common problem but it didn't fix it. Then I tested the fan by hooking it straight to the battery and it kicked on full speed so it's not the fan. I also tested the connectors and everything is fine.

My question is whether the coolant temp sensor could be the problem. I assume that's what the computer reads to know to turn the fan on. I just can't think of anything else it should be.

__________________
www.norcaljeepers.co
CMARJEEP is offline   Reply With Quote
Unread 05-03-2013, 03:08 AM   #2
cykaaro
Registered User
2000 WJ 
 
Join Date: Apr 2012
Location: orangville, ON
Posts: 2,804
Does the fan come on when you put the A/C on?
__________________
The beatings will continue until attitudes improve!

HID Quad bi-xenon + foglight retrofit
http://www.hidplanet.com/forums/showthread.php?44572-Jeep-2000-Grand-Cherokee-WJ
cykaaro is offline   Reply With Quote
Unread 05-03-2013, 03:15 AM   #3
CMARJEEP
Registered User
2001 WJ 
 
Join Date: Aug 2007
Location: Sacramento, CA
Posts: 2,672
Quote:
Originally Posted by cykaaro View Post
Does the fan come on when you put the A/C on?
No. I've been reading that it should come on with the A/C though no matter what the engine temp is correct?
__________________
www.norcaljeepers.co
CMARJEEP is offline   Reply With Quote
Unread 05-03-2013, 04:24 AM   #4
Mhancock2
Registered User
2004 WJ 
 
Join Date: Mar 2013
Location: Indianapolis, Indiana
Posts: 51
There is a relay that is known for blowing on these. All the manuals tell of a long process to get to the relay. YouTube it and they show a much easier way. I believe it is behind the oassenger's side headlight.
Mhancock2 is offline   Reply With Quote
Unread 05-03-2013, 09:26 AM   #5
metalhead
Registered User
2000 WJ 
 
Join Date: Nov 2008
Location: southampton, Pa
Posts: 950
If the coolant temperature sensor is bad you would get a check engine light and most likely the engine would run rich. May be something in the wiring.
metalhead is offline   Reply With Quote
Unread 05-03-2013, 11:03 AM   #6
Highschool_WJ
Registered User
1999 WJ 
 
Join Date: Jan 2013
Location: Minot, ND
Posts: 237
when is the last time you replaced the thermostat?
Highschool_WJ is offline   Reply With Quote
Unread 05-03-2013, 11:31 AM   #7
CMARJEEP
Registered User
2001 WJ 
 
Join Date: Aug 2007
Location: Sacramento, CA
Posts: 2,672
Quote:
Originally Posted by Mhancock2 View Post
There is a relay that is known for blowing on these. All the manuals tell of a long process to get to the relay. YouTube it and they show a much easier way. I believe it is behind the oassenger's side headlight.
Did you even read my first post? I already replaced it. The problem is the fan. The relay is good. The fan is good. The wiring is good to the fan. I'm trying to figure out what triggers the fan to turn on.
__________________
www.norcaljeepers.co
CMARJEEP is offline   Reply With Quote
Unread 05-03-2013, 11:41 AM   #8
metalhead
Registered User
2000 WJ 
 
Join Date: Nov 2008
Location: southampton, Pa
Posts: 950
The pcm triggers the fan to turn on using data from the coolant temperature sensor. There is also 2 fuses for the fan. A 40 amp fuse in the power distribution block and a 15 amp fuse in the junction block.

Last edited by metalhead; 05-03-2013 at 11:50 AM.. Reason: more info
metalhead is offline   Reply With Quote
Unread 05-03-2013, 11:54 AM   #9
4Tom
Registered User
2001 WJ 
 
Join Date: Mar 2011
Location: Dublin, Ireland
Posts: 2,460
Engine control module turns on the fan.
Either because your temperature is high or AC is switch on.

Its not unheard of having a faulty new relay. They are very difficult to test because its a electronic controled relay and its output is pluse width modulation
The wider the pluse the faster the fan spins. Its a 12v pluse but a DC meter won't read it.

Ossiliscope could measure the output but very few of us have one so an ac meter might give you an indication of 6 to 8 ac volts.

The most common problem is the relay and repeated relay failure is worn fan.
Connecting the fan to battery doesnt tell you if the fan is worn or drawing too much current blowing relay. It only a crude check fan will spin with power.

I haven't tried it but believe if the tempture sensor is disconnected the fan should spin full speed. Although as yours isnt working with AC either I suspect you have faulty new relay or damaged wiring connection going to fan.
__________________
WJ 2001 3.1TD
http://www.jeepforum.com/forum/f22/2001-wj-3-1td-1252959/

Tom
4Tom is offline   Reply With Quote
Unread 05-03-2013, 10:10 PM   #10
CMARJEEP
Registered User
2001 WJ 
 
Join Date: Aug 2007
Location: Sacramento, CA
Posts: 2,672
Thanks metalhead and 4tom, that's the info I was looking for.
__________________
www.norcaljeepers.co
CMARJEEP is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.