2002 Grand Cherokee engine fan won't turn off

Messages
2,120
Location
Southeast Michigan
Hi guys. My girlfriend has a 2002 Jeep Grand Cherokee with 220K miles on it. Her battery died today and she got it replaced with a ProStart at Pep Boys. But apparently now her engine cooling fan won't shut off, even when she turns the vehicle off. She had to disconnect the battery. Does anyone know what this might be? Would prefer to have an idea before she takes it in. Thanks.
 
Messages
774
Location
A Warm place to live in
Many years ago, I was called up by my sister-in-law to fix exactly this problem in her car. Lazy sloth that I am, rather than troubleshoot the whole thing, and that it wasn't even my car, I just wired a heavy duty on-off switch in series with the fan wiring. I put that switch near the dash and told her to turn it on before she started the engine, and turn it off after she shut it down. She used my "There I Fixed It" solution till she sold the car years later.
 
Messages
1,464
Location
Gulf Coast, MS
Easy fix is just run the positive from the fan to the fuse box. Friend did this in a old neon. It will run 100% while the cars on but its better then not turning off.
 
Messages
774
Location
A Warm place to live in
Originally Posted By: 3800Series
Easy fix is just run the positive from the fan to the fuse box. Friend did this in a old neon. It will run 100% while the cars on but its better then not turning off.
Great idea! But didn't he have to replace the fuse where he taps the power with a bigger ampere rating to keep it from blowing with that added electrical load?
 
Messages
36,473
Location
ME
This probably has the "soft start" solid state relay that is pricy from ma mopar. Are we sure someone didn't try, perhaps incorrectly, to jump start the thing?
 
Messages
693
Location
PA
Ive had this more times than I can count...... It IS your fan control relay, it's a PWM relay (please do yourself a favor and DONT HARD WIRE IT). The relay is located under the passenger side headlight fixture, you will need to cut a "trap door" in the bumper cover (hidden from view) to access the relay, than one bolt and a plug, I ALWAYS buy that relay at NAPA and utilize there lifetime replacement because it will go again in 2 years. If you need more info about getting to the relay I can help, its not as bad as it sounds to get to.
 
Last edited:
Messages
14,737
Location
Central NY
Usually when the fan relay goes out, it stops working alltogether. It's probably the PWM as noted above. If it was only doing it when the vehicle was running, I'd also recommend making sure the gauge works and that it didn't lose the coolant temp sensor.
 
Messages
8,049
Location
Mahzurrah!
As noted above, these models are notorious for bad relays. They usually quit though, never the less I'd start there and be really surprised if it doesn't fix it. It probably has two, my 04 does. A low and a high.
 
Messages
159
Location
North TEXAS
Don't hotwire the fan -Fix it correctly - running the fan all the time will wear it out in short order, then then engine will overheat and blow head gasket or crack head.
 
Messages
1,464
Location
Gulf Coast, MS
Theses relays can be quiet expensive. I don't personally know about the Jeeps but iv replaced them in my car and they have cost well over $100 for a single relay. The argument about it killing the fan is a insanely over exaggerated. Fact is if you start the car and drive for 30 mins the fan will kick on in 5 mins and will run for 25 mins. Running it with it wired to the fuse box and drive it for 30 mins and it will run for 30 mins. The idea that it will be a major failure is really a joke. Theses fans are meant to last the life of the car and spend 90% of the time on while the vehicle on. The difference in the fan kicking on when the car turns on or it kicking on 5 mins after the car is on will lead to very little stress on the fans. My buddy has had it done for over 7-8 years and it still works perfectly fine. By all means tho if your sister wants to pay for the relay and you don't mind going threw the trouble of installing it then do it that way. I'm just trying to help someone save a dollar. Nothing wrong with that.
 
Messages
6,164
Location
Illinois
Actually the fans usually shut off for engine cooling after 30-35 mph. The AC hi speed fan will run any time the pressure gets too high after the condenser.
 
Messages
693
Location
PA
Originally Posted By: 3800Series
Theses relays can be quiet expensive. I don't personally know about the Jeeps but iv replaced them in my car and they have cost well over $100 for a single relay. The argument about it killing the fan is a insanely over exaggerated. Fact is if you start the car and drive for 30 mins the fan will kick on in 5 mins and will run for 25 mins. Running it with it wired to the fuse box and drive it for 30 mins and it will run for 30 mins. The idea that it will be a major failure is really a joke. Theses fans are meant to last the life of the car and spend 90% of the time on while the vehicle on. The difference in the fan kicking on when the car turns on or it kicking on 5 mins after the car is on will lead to very little stress on the fans. My buddy has had it done for over 7-8 years and it still works perfectly fine. By all means tho if your sister wants to pay for the relay and you don't mind going threw the trouble of installing it then do it that way. I'm just trying to help someone save a dollar. Nothing wrong with that.
The fan motor in WJ is a bit different, and WILL go bad running it at full speed (passing full current demand) the point of the PWM relay is to limit this based the demands from ECM. the relay is around $45. The relay has nothing to do with the amount of time the fan run its about the fan speed based on what the coolant temp sensor tells the ECM. The other side of this is emissions, the 4.0 JEEP motor is designed to function @208-210F, and with the fab running full blast at start-up it will take the engine that much longer to reach the spec'ed temp causing the engine to run rich and diminishing fuel economy and insuring the early failures of O2 sensors. NOTHING in a JEEP is meant to last the lifetime of the vehicle other than 4.0 ! since they last 300K mi lol ! There is always a reason to fix something the proper way and allow the vehicle systems to work as it should in modern systems.
 
Messages
13,058
Location
Indiana
Originally Posted By: 3800Series
Easy fix is just run the positive from the fan to the fuse box. Friend did this in a old neon. It will run 100% while the cars on but its better then not turning off.
I don't recommend this at all. This will cause the fan to prematurely fail.. then you'd be without a fan completely. The fan hardly runs as it is depending on speed (air flow). OP: Next time this happens, just disconnect the cooling fan fuse that's in the fuse box on the front passenger side. Much easier than the battery IMO. Its definitely a stuck fan relay. This is how I fixed mine. Takes all of 20 mins now. https://www.youtube.com/watch?v=E5K1D1iEQO8 I bought mine from Oreillys for about $40-$50 with a lifetime warranty.
 
Messages
5,651
Location
Iowa
Yes, please don't hotwire the fan! It's about 55-60 dollars for the relay (ECH AR473) from NAPA and better than having to rely on someone to turn a fan off and on. I learned that at a young age when I built a warmed up engine for a fellow to go in his Camaro. Well, he had an electric cooling fan on a toggle switch and forgot about it one morning while letting the car high idle in the drive. He said it boiled the coolant out and got to 250* or 260*!!! After that, I put a mechanical fan and shroud on it, that way he wouldn't have to be relied upon to remember.
 
Top