jeep a/c fan motor runs on

cdchatfield · 11-28-2008, 07:00 AM

I've got a 2001 Jeep Cherokee 4.0. The underhood a/c fan occasionally comes on and continues to run after the car is turned off. This is November and neither the a/c nor defrost were in use.
I have had the relay replaced and the wiring checked for shorts. Still happens. If I pull the fuse, it stops but starts again when the fuse is re-installed. If I pull the relay, it stops and does not continue when I replug it.
Any ideas?

dodgemechanic · 11-28-2008, 09:03 PM

There is an ac pressure transducer in the ac line on some of these models and if that switch/sensor goes bad, it can make the AC fan stop working...on the flip side to that...I've seen in two cases where it's made the ac fan come on. Try finding the switch/sensor in the line and unplugging it when the fans kick on. If it goes off..there you go. If not, I'm not sure if that year had an AC module or not but unfortunately you probably don't have access to a DRB to check the system. I guess with limited resources I would go to the parts store and check out a book on the vehicle and trace the wiring diagram for the AC fan. Good luck. If you give the last six of your vin, I might be able to help you more.

**mack1** · 11-28-2008, 10:01 PM

Hi cdchatfield and welcome to TSF

I'm probably the only one that don't know what an "underhood a/c fan" is. Is that an electric fan that survices only the condenser coil? Normally radiator and condenser coil are cooled by the same fan, belt driven or electric motor. The point being that the heat sensor in the block turns those fans on/off and I was wondering what sensor tells the a/c fan to turn on.

Quote:

If I pull the fuse, it stops but starts again when the fuse is re-installed. If I pull the relay, it stops and does not continue when I replug it.

This is interesting. First sentence sounds like the relay contacts are welded together. Second sentence sounds like the relay contacts are not welded together.

If you have some electrical prints of this circuit, please post them. I'd like to help you solve this contradictory problem.

How to post prints is described in this article:

http://www.techsupportforum.com/cont...icles/151.html

Best regards,
Mack1

dodgemechanic · 11-30-2008, 09:26 PM

After reviewing your vehicle in the Chrysler computers, I've discovered that your vehicle has a simple radiator fan motor-the wiring being as simple. It runs from the battery to the power distribution center to the relay to the motor. The PCM does have input so that might have something to do with that, but if you could pull codes, you should see some sort of problem. Your local parts store might offer that free service to you.

11-28-2008, 07:00 AM	#1 (permalink)
cdchatfield Registered User Join Date: Nov 2008 Posts: 1 OS: xp	jeep a/c fan motor runs on I've got a 2001 Jeep Cherokee 4.0. The underhood a/c fan occasionally comes on and continues to run after the car is turned off. This is November and neither the a/c nor defrost were in use. I have had the relay replaced and the wiring checked for shorts. Still happens. If I pull the fuse, it stops but starts again when the fuse is re-installed. If I pull the relay, it stops and does not continue when I replug it. Any ideas?

11-28-2008, 09:03 PM	#2 (permalink)
dodgemechanic Registered User Join Date: Nov 2008 Posts: 5 OS: windows xp	Re: jeep a/c fan motor runs on There is an ac pressure transducer in the ac line on some of these models and if that switch/sensor goes bad, it can make the AC fan stop working...on the flip side to that...I've seen in two cases where it's made the ac fan come on. Try finding the switch/sensor in the line and unplugging it when the fans kick on. If it goes off..there you go. If not, I'm not sure if that year had an AC module or not but unfortunately you probably don't have access to a DRB to check the system. I guess with limited resources I would go to the parts store and check out a book on the vehicle and trace the wiring diagram for the AC fan. Good luck. If you give the last six of your vin, I might be able to help you more.

11-30-2008, 09:26 PM	#4 (permalink)
dodgemechanic Registered User Join Date: Nov 2008 Posts: 5 OS: windows xp	Re: jeep a/c fan motor runs on After reviewing your vehicle in the Chrysler computers, I've discovered that your vehicle has a simple radiator fan motor-the wiring being as simple. It runs from the battery to the power distribution center to the relay to the motor. The PCM does have input so that might have something to do with that, but if you could pull codes, you should see some sort of problem. Your local parts store might offer that free service to you.