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2003 Jeep Grand Cherokee Laredo 4.0 4x4
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Discussion Starter · #1 ·
Hello. This is my first post. Ive read every post I could find on this forum and others on this subject and have not seen it discussed yet: Can the factory fan controller control an aftermarket electric fan?
Im aware of what the PWM is and does and how its different from a normal fan relay. But, it seems to me that it would just vary its output and control an aftermarket fan based on the same parameters as it would the factory fan? So long as the amperage draw of the aftermarket fan was equal to or less then the stock fan of course. Thoughts?

P.s. I also understand that most people tend to bypass the stock controller because it fails.
 

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2017 Summit, California Edition Hemi
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I don't see why it wouldn't work. I have aftermarket fans on my car and I'm using an aftermarket PWM controller on them. What I'm curious to know is why you want to swap out the original fan for an aftermarket one? If it's bad, you'll be much further ahead to replace it with another on because most aftermarket fans are junk. They don't move as much air, are loud and generally won't last as long. In the hot rodding world, the guys who have been there and done with aftermarket fans try to use OEM fans as much as possible because they're far better.
 

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2003 Jeep Grand Cherokee Laredo 4.0 4x4
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Discussion Starter · #3 ·
I don't see why it wouldn't work. I have aftermarket fans on my car and I'm using an aftermarket PWM controller on them. What I'm curious to know is why you want to swap out the original fan for an aftermarket one? If it's bad, you'll be much further ahead to replace it with another on because most aftermarket fans are junk. They don't move as much air, are loud and generally won't last as long. In the hot rodding world, the guys who have been there and done with aftermarket fans try to use OEM fans as much as possible because they're far better.
Whats the CFM rating on the stock fan? Whats its amperage draw? Cant seem to find that info anywhere either.
 

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2003 Jeep Grand Cherokee Laredo 4.0 4x4
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Discussion Starter · #4 ·
Side note: Ive had this WJ for a year. I bought it because bringing my dog to the beach in my C6 was a little too stressfully for us both. Even with its few well known bugs, I absolutely love this thing. It is exactly what I needed. Handsome, comfortable, and reliable canine transport.
234701
 

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2017 Summit, California Edition Hemi
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No, most likely you won't find the cfm rating unless someone tested one. The amperage draw can be done with a proper DVOM. There's tons of them in pick a parts if you need a fan assy.
 

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Questions??
What engine do you have? How many miles?
And why exactly are you concerned about the fan? Over heating?
Is this a hydraulic fan or an efan?

If its an over heating issue IMO the PWM type modulation hydraulic fan is next to junk with an older hi mileage vehicle.
If its an over heating issue which you don't say then i'd jury rig an efan fan full balls or off....plenty of kits out there.

If it is indeed an overheating issue please say so.
Maybe there's some other things that can help.
 

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2003 Jeep Grand Cherokee Laredo 4.0 4x4
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Discussion Starter · #7 ·
4.0 4x4. Mine has both efan and mechanical. No overheating.
So theres no reason the stock PWM "relay" wouldnt run any 12v electric fan i.e. turn it on and off at the right temp, or when the AC is on, and vary its voltage ect?
 

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4.0 4x4. Mine has both efan and mechanical. No overheating.
So theres no reason the stock PWM "relay" wouldnt run any 12v electric fan i.e. turn it on and off at the right temp, or when the AC is on, and vary its voltage ect?
Ok more facts now.
Are you concerned about the efan or its relay? Please explain in more detail.

The 4.0 is notorious for over heating in grid lock city traffic or standing in McDees drive throughs but i'm not hearing any of that from you.

PWM is just that it varies the DC duty cycle to a DC motor to control its speed which far as i know all efans utilize a DC motor. So if you want to replace the efan with something better? i'd think any of them are good to go.

I'm still confused, if its not overheating why are you concerned about i think you're saying another efan replacement?
Is it just a PM efan replacement?

So far in my hard head i'm really really not getting this.
 

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2003 Jeep Grand Cherokee Laredo 4.0 4x4
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Discussion Starter · #9 ·
Thank you for your replies. Dont mean to seem cryptic, but threads so quickly can go off on a another tangent, so I try to keep my questions specific. A fact finding mission as opposed to a discussion.

I am curious about a few things about these notorious WJ fan controllers that I have not seen discussed in the many threads Ive read. It seems everyone either replaces the relay (and OEM fan also sometimes, because a worn fan may toast the PWM is my understanding) each time it fails or they bypass it with a normal relay. I noticed that people only seem to attempt to upgrade the fan when they use a regular relay. I havent seen anybody try to run a different 12v fan on the stock controller ,nor even seen it discussed, so I simply wondered if there was a reason for that.
Also as Ive stated Ive never seen anyone refer to any specs (CFM, Amp draw) for the stock fan so I was inquiring about that also.

Another question: Could you substitute an aftermarket PWM type controller like Mopar Guy mentioned; for our problematic OEM one? Would the WJ computer notice, or just run the fan normally?

Again, my Jeep is fine, but like eveybody else Ive had to replace the little fella, so it makes me curious.
 

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Thank you for your replies. Dont mean to seem cryptic, but threads so quickly can go off on a another tangent, so I try to keep my questions specific. A fact finding mission as opposed to a discussion.

I am curious about a few things about these notorious WJ fan controllers that I have not seen discussed in the many threads Ive read. It seems everyone either replaces the relay (and OEM fan also sometimes, because a worn fan may toast the PWM is my understanding) each time it fails or they bypass it with a normal relay. I noticed that people only seem to attempt to upgrade the fan when they use a regular relay. I havent seen anybody try to run a different 12v fan on the stock controller ,nor even seen it discussed, so I simply wondered if there was a reason for that.
Also as Ive stated Ive never seen anyone refer to any specs (CFM, Amp draw) for the stock fan so I was inquiring about that also.

Another question: Could you substitute an aftermarket PWM type controller like Mopar Guy mentioned; for our problematic OEM one? Would the WJ computer notice, or just run the fan normally?

Again, my Jeep is fine, but like eveybody else Ive had to replace the little fella, so it makes me curious.
OK got it!
A disclaimer, I'm not familiar with the so called PWM controlled efans in your Jeep.
Might want to go on line and find a schematic of the efan system for your model and year Jeep.

Unless the efan has some kind of specialized motor with multiple stator tap wires going into it to step control its speed which i highly doubt then it would need a step controller or in the least multiple relays.
Or as with some HVAC blower motors, their speed is controlled by stepping in certain resistors to reduce the motor's voltage via a switch or relays to step control the motor's speed.
If either of the above, then 'PWM' is a mis-nomer.

If the efan motor only has two wires going into it AND its speed can vary linearly from 0 to max rated rpm then its speed is varied by a true PWM system.
Having said that, the controller could also step the motor's speed by incorporating various pre-defined duty cycles to step increase or decrease the average voltage to the motor.

The benefit of PWModulated motor speed control is efficiency meaning it wastes less energy as opposed to a resistor based speed control.

Far as answering some of your questions if its a true self contained PWM controller then that involves a lot of expensive electronic circuitry to pull it off.
More than likely the PCM's software controls the duty cycles to the controller with the controller being only an interface to supply PWModulated B+ voltage to the efan motor sort of a high amperage amplifier.
Anyhow thats how i would design the system to reduce cost.

I would think any efan would work with the OEM system as long as its max. amperage rating is within the controller's max. amperage spec.
Finding that spec. is the problem.

Some people might install an aftermarket efan with a much higher cfm and amperage rating which could toast the controller. That could be the reason they bypass the controller with a efan ON/OFF jury rigged relay controlled by a switch or a temperature control system which is available over the counter.
However if the OEM controller is completely toasted i'd think that would throw a CEL.

Getting any kind of max amperage specs for aftermarket or OEM efans can be a challenge.
CFM ratings though are much more easier to come by for at least aftermarket efans.
At one time i was thinking on replacing my XJ's efan with a higer CFM rating but for the life of me i could not find the stock OEM CFM rating for comparison.
 

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I just bypassed the PWM controller IE left the Ground hooked up but capped off the 2 wires for it no CEL. I also used the OEM fan and just wired it directly in with a 50amp Relay and Inline fuse. IE she's 1 speed now Max Inrush Amperage on mine was close to 41amps dc then chills out around 28-30amps. Then I got simple Switch on the dash kick it on Makes that Durango Alternator on my 4.7 Work. Only time i use it is when I am putting around town with the A/C on Does wonders for your AC while sitting at idle getting rid of that heat off the condenser. While on high or at speed I turn it off

Side note my Mech clutch fan was bad IE could stop it with my a news paper at any temp. I do not recommend replacing with an HD Clutch unit most places store because the Mfer never unlocks and only does if you floor it for a few seconds and cruise at 3 or 4k rpm.
 

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2003 Jeep Grand Cherokee Laredo 4.0 4x4
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Discussion Starter · #13 ·
I just bypassed the PWM controller IE left the Ground hooked up but capped off the 2 wires for it no CEL. I also used the OEM fan and just wired it directly in with a 50amp Relay and Inline fuse. IE she's 1 speed now Max Inrush Amperage on mine was close to 41amps dc then chills out around 28-30amps. Then I got simple Switch on the dash kick it on Makes that Durango Alternator on my 4.7 Work. Only time i use it is when I am putting around town with the A/C on Does wonders for your AC while sitting at idle getting rid of that heat off the condenser. While on high or at speed I turn it off

Side note my Mech clutch fan was bad IE could stop it with my a news paper at any temp. I do not recommend replacing with an HD Clutch unit most places store because the Mfer never unlocks and only does if you floor it for a few seconds and cruise at 3 or 4k rpm.
Thanks. Thats yet another configuration I have not read about anybody trying. This is the sort of info Im looking for. I did notice that although my entire AC is 100% new, there was a definite temp variance at idle. I think its pretty obvious that our WJs have barely adequate airflow through the rad at idle. That is why even the manual admits the temp will begin to creep up at idle under certain conditions. Even mine, which has BOTH mech and electric fans. And since the mech fan isnt a factor at idle, it all points to the elec fan being JUST barely adequate.
Wow, that little fan pulls some serious amperage. I wonder if thats just what those fans normally pull or if yours just pulled a little more because its mileage.
Anyways, like I said, minor flaws aside, I really like my GC. My dog loses her mind whenever she sees me drive off with her Jeep wihout her.
 

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I just bypassed the PWM controller IE left the Ground hooked up but capped off the 2 wires for it no CEL. I also used the OEM fan and just wired it directly in with a 50amp Relay and Inline fuse. IE she's 1 speed now Max Inrush Amperage on mine was close to 41amps dc then chills out around 28-30amps. Then I got simple Switch on the dash kick it on Makes that Durango Alternator on my 4.7 Work. Only time i use it is when I am putting around town with the A/C on Does wonders for your AC while sitting at idle getting rid of that heat off the condenser. While on high or at speed I turn it off

Side note my Mech clutch fan was bad IE could stop it with my a news paper at any temp. I do not recommend replacing with an HD Clutch unit most places store because the Mfer never unlocks and only does if you floor it for a few seconds and cruise at 3 or 4k rpm.
Holy smokes, 41 Amps. Must be one hell of a motor.
Thats likely one of the reasons they designed in a PWM speed control system.
The OEM efan on my XJ uses a 20 Amp fuse. Its either a binary full balls on or off.

Speaking of the clutch fan,
I upgraded the stock clutch fan on my XJ with a ZJ clutch fan which is a heavier duty clutch fan.
It made no difference with prolonged idle overheating in hot weather.
A waste of time, money and HP.

What i did notice is the flimsy OEM clutch fan shroud design in my XJ is junk.
The fan blades are nowhere contained inside the shroud which means instead of pulling air through the radiator it just recirculates the stagnant hot air in the engine compartment.
Maybe thats by design but i can't think of any logical reason.
One of these days i'm gonna replace that shroud with something more efficient.

On the other hand the OEM efan's shroud fully contains the fan blades.
When i turn it on with my manual switch setup when i see the temp rising during idling, it immediately brings the temp back down to the thermostat setting in a matter of a few minutes.
 
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