Electric fan is not coming on at all, checked fuse and it was fine, disconnected fan and checked for power at fan, had no power, is there a relay? If so where can I find it? what controls the fan? Is there a temperature switch?
The electronic fan relay on this model fails very often, causing the problem you describe. I attached a picture of the location.
is there a fuse that controls the relay?
no, the relay is not really a relay
its a PWM modulator.
it's is a high powered 30+amp transistor and a pre-amp in front. (im an ET, hint, my bag)
the PCM modulates it at all times.
but there are fuse for the PCM. but if those blow, far worse happens.
do you need the schematic, its really boring.
to test the DEVICE takes a scope
0v out its dead
12out its at 100 percent.
if at 50 % duty cycle, some DC volt meters read 7v out(1/2 battery = 50%)
a scope always works but some meter can do this.. many cheap ones not...
its a Pulse width modulator with an alternating square wave out.
it works almost the same as all injectors on all MPI engines.
same... (but way more current)
if wanting to check fuses
we use a voltmeter and check each one
for 12vdc on both sides.
some fuses look good and are NOT.
Good diagram. Seen some cases of overheating as well due to faulty fan or fan relay.
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Had this happen on my Jeep. There is a Solid State relay located underneath the passenger front headlight. Most major auto parts stores carry the relay. Unfortunately, you either have to take the front bumper off and the passenger headlight off to get to it, or take your headlight out, and cut a hole through the metal under the light to get to the relay. I opted to just take the bumper off. Really simple fix, just a pain to have to take bumper off.
I change my rad fan relay once a yaer like clockwork. Four of them n the last three years. I removed the right headlamp assembly and using a 4 inch hole saw drilled carefully through the plastic underneath. You can change relay in about 5 minutes after that. Use a piece of rubber and a couple of rivets to cover the hole and re-install headlamp assy. Garage wants about 6 hours labour to change th relay.
that is my act too, hidden access points.
bravo.
a super idea this.
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I have the same problem with my jeep. Talked with a dealer and was told that it is because they don't get enough air to cool down. So I went to my local auto parts store and got all the colors of wire,somebutt connectors with heat shrink, wire ties and a piece of wire loom. I went down to the relay gave myself enough wire to work with, about 3 inches from the relay connector and cut each wire, remember that their is power in the wires so don't cut at one time, Add enough wire to mount the relay up on the fire wall so that it gets more air flow to cool off. Now use **** connectors with heat shrink to seal out the weather or you are asking for trouble down the road. Now put on the wire loom around the harness you just made and tie off harness in safe areas. This make it easier to change not time if you have to. Two years and going strong with this fix.
even better idea, keep it cool.
and my idea add a heat sink to it.
cut the wires battery neg lug removed,
this is SOP , standard op procedures..
or make me rich, (will before i retired.)_
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That flat spot, #2 screams to me for a heat sink.
keep it cool and it might last 20 years.
Hi guys. for all of you that are having problem with this fan sensor, that not only fails often but can put the vehicle in a severe overheated condition and cause you to spend lot of momey in an engine overhaul. This is what i have done and never ever have an overheated engine. I simply replaced the electric fan with a slip clutch fan. Easy to istall and good bye to this problem. Hope all you cherokee owners Happy motoring
which engine? 4.0L has elect (not 4.7l hydr)
its a hybrid fan (clutch fan and electric)
the clutch fan engages at 195 to 205F)
the electric is another matter.
it's a PWM modulated fan. (see FSM say so...)(
THE PCM modulates this fan PWM relay(sic)
it's no relay but a transistor and pwm receiver. if min overheated(the module)
i'd add a heat sink to mine. easy, ask.
as you know heat kills electronics fast...
the PCm uses (this inputs to modulate this fan)
ECT temps (engine too hot?)
ambient BCM temp
veh. speed
tranny oil temp
and A/C requests to run this fan.
off, is one condition,
(to keep noise down)
the PWM fan is used to keep noise down in all modes but gross overheated (by design)
bypass.?(theory but risky)
or add a $2 switch called bypass.
see overheating to start so throw switch, until time to drill above hole, per above poster. and fix this failure
the part is (WJ JEEPS)
Radiator cooling fan relay is (pulse width modulated) 1 wire from PCM to so called relay)(near infinite speeds possible)
I'm not sure if hot wiring the relay is safe to it, or for the fan or relay.
some devices PWM are ok at 100% duty cycle rated;
my guess is the fan is ok with that.
(never injectors for example)
in a pinch,
id put the hole there (posters idea prime), for easy access
and then make jumper plug that fits the relay socket so I can drive safely home
and fix it proper.
the module? (still good or new), id add a heat sink
with the special thermal heat sink epoxy.
first used that 1976, (yah , im old)
id bet it wont fail then....
if kept cool.
In life testing electronics, we used heat.
so avoid it.
my guess at 120F in Phoenix, with A/C on
and duty near 50% this part fails soon.
that is my bet.
heat sink it or move it. to fresh cold air flow area, (front grill tops list)
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Hi is it the 4.7 v8 if so u need to check your viscos fan hub to make sure its engaging with the motor off spin the fan there should be some resitance but if there is none and fan spins freely then u need to replace the fan hub.
he failed (as most ) post the engine size
but the 4.0 is the only hybrid version per the FSM. the 4.7 has a hydraulic fan sys.
but for the 4.0L the clutch fan is first
but my guess is he overheated the engine
and when , gee, my electric fan is dead.
my guess..
the 4.7 has hydraulic fan. and electric.
both must work right but his fails on the electric fan side. and that is a bad fan modulator relay(sic) (module is the correct word)
the unit overheats and dies.
the cooling chapter is free to read.
http://www.jeep4x4center.com/knowledge-b...
posted 100s of time, this book.
even shows where the parts are, and schematics
the 4.7L
power steering pump , powered hydra. motor there. if this fails and the elect fan, OH boy....
the E fan, works like your home, ceiling fan
with a wall mounted PWM controller.
you turn the knob CW and Duty cycle goes up.
and fan spins faster.
in the case if this car, the knob is a brain
the PCM brain, it has just one wire
and controls the modulator at all times.
this jeep is not a 1993 JEEP.
on this jeep the PCM makes all the decision here, ALL. (well cept fan clutch and hydr. fans)
page 41, cooling chapter.
step1 bumper and grill off..
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SOURCE: 2001Jeep Grand Cherokee electric engine cooling fan wont turn off
relay sounds stuck...call a parts store for pricing
SOURCE: i need to locate the relay for the electric fan in
its located behind the right headlight ,thier is a plastic shied in front of it and its hard to remove i usually take a saws all and cut around the piece to get it out the i R T V or caulk it back in since you cant ever see it anyway, thats what they do at the dealer.
SOURCE: 2001 jeep grand cherokee laredo
suggest that you rent a pressure tester from auto zone or advance auto and preform a pressure test on your cooling system. follow the instructions on the test of pressure to your cooling system,also check for coolant leaks onto the ground from radiator area. may be bad water pump,broken hose,heater hose,upper radiator,lower radiator,or a bad radiator itself. a simple pressure tester will reveal the coolant leak. but make sure to follow the instructions with the pressure tester,as you can damage your coolant system otherwise. thank you for choosing fixya.com
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FAN NOT COMING ON VEHICLE IS OVER HEATING RELAY HAS CURRENT GOING THROUGH MOTOR IS GOOD WHAT ELSE COULD IT BE?
2001 Jeep Grand Cherokee
Fan fuse is good but no power to the fan.
Noticed the car overheating at a stop light. I begun to drive and the temp dropped to normal all the way home. Got home and the temp rose again and noticed the fan wss not running even with the AC on? I took to the dealer and they say the fan works and the car is not over heating and suggested a thermosat change? Could it be a intermittent fan relay switch problem?
my jeep was overheating to because my fan wasn't working it was a relay it was like a $80.00 part!
cooling fan will not run and it over heats. test fan and it will run if I put power to it. I can not locate the relay but the fuse is good.
my 2000 Jeep cherokee overheats only in town not on the highway, i take it because air is getting to it, i was told probably fuse when i had a garage look at it which they dont do that kind of work , the dealer told me i need a new fan motor, going to check around before i put 2 or 3 hundered dollars in it to be sure. Air stays cold until i slow it down so i have to turn the air off until i get back on the highway, what a pain.
Same problem with mine but does not have sensor attached to wire hook up. Been in two wrecks to where replacement of radiator and front end have had to be replaced. Is there supposed to be relay??
overheating when idleing fan does not come on where is the relay switch located
Have replaced "EVERYTHING" but the fan. The fan works sometimes, by that I mean if the A/C switch is on it will come on. Sometime it will come on when engine temp is at about 210, but since it is not my car and I am helping a friend who is out of the country, I am only told what is wrong by the wife driving it. I have had it over heat on me after replaceing the thermostat. I have replaced the Fan relay, Thermostat, Water Pump, Radiator Cap. I understand the fan is a multispeed fan and requires only about 6 volts to get it running on low, and 12 volts being the high speed. Is the Fan a brushless fan or are there brushes internally that are getting worn and should the fan be replaced.
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