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Discussion Starter · #1 ·
I have a 2014 Jeep Grand Cherokee, 4WD, tow package, V8 Hemi. The high speed fan is not coming on when the AC is on as it normally does. I checked the power to the High and Low speed fan relays; the control pins are hot (to turn on the relays), and the power to the relays is hot (so power is going through the relays). I also tried a jumper across the relays, to provide power directly to the fan. No change in fan speed with either relay. Interestingly, if I remove both High and Low speed relays, the fan will continue to run - perhaps there is a backup in case both relays fail.

I would like to get the fan running at high speed when the AC is on, as summer is coming and I tow a trailer. I'm starting to think that the fan needs to be replaced, but I'd like to do more tests to confirm this before dropping $400 on a new fan. Are there other fuses somewhere, perhaps a fuseable link? Looking at pictures of replacement fans (see attached), I notice that there is a large resistor on the back of the fan near some sort of module - any idea what the resistor is for? Any advice is appreciated. - Charlie

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Jeep likes to confuse us amateurs. SD cooling has a two speed fan with relays. The HD cooling fan does not use the relays, but I think it throws a fault if they are not installed. The HD fan has a battery, ground, and control signal connections. The speed control comes from the PCM through the TIPM. There are more than two speeds, its variable. I think there are a couple HD cooling diagnostic threads around here somewhere, but it may take me some time to find them. A full feature scanner can set the fan speed to verify operation, or read any diagnostic codes present.

There are three inputs to the PCM that determine what speed percentage of fan is required by the vehicle. These inputs are:
  • Engine Coolant Temperature
  • Transmission Oil Temperature
  • A/C System Pressure

By monitoring these three parameters, the PCM can determine if cooling airflow is required. If airflow is required, the PCM will send a signal to the fan module to slowly ramp up (speed up) the fan speed until the parameter(s) are under control. Once the temperature is reduced to within operating parameters the fan will ramp up, ramp down, or hold its speed to maintain the temperature requirements, while reducing unnecessary power drain on both the engine and the vehicles electrical system and keeping the NVH of the fan low.

Normally the fan won't ramp up when turning the A/C on unless the A/C pressure indicates it needs extra cooling. There may have been an unrelated fault causing what you thing is normal operation that has now progressed to another state..





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Discussion Starter · #3 ·
Jeep likes to confuse us amateurs. SD cooling has a two speed fan with relays. The HD cooling fan does not use the relays, but I think it throws a fault if they are not installed. The HD fan has a battery, ground, and control signal connections. The speed control comes from the PCM through the TIPM. There are more than two speeds, its variable. I think there are a couple HD cooling diagnostic threads around here somewhere, but it may take me some time to find them. A full feature scanner can set the fan speed to verify operation, or read any diagnostic codes present.

There are three inputs to the PCM that determine what speed percentage of fan is required by the vehicle. These inputs are:
  • Engine Coolant Temperature
  • Transmission Oil Temperature
  • A/C System Pressure

By monitoring these three parameters, the PCM can determine if cooling airflow is required. If airflow is required, the PCM will send a signal to the fan module to slowly ramp up (speed up) the fan speed until the parameter(s) are under control. Once the temperature is reduced to within operating parameters the fan will ramp up, ramp down, or hold its speed to maintain the temperature requirements, while reducing unnecessary power drain on both the engine and the vehicles electrical system and keeping the NVH of the fan low.

Normally the fan won't ramp up when turning the A/C on unless the A/C pressure indicates it needs extra cooling. There may have been an unrelated fault causing what you thing is normal operation that has now progressed to another state..





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Discussion Starter · #4 ·
Thanks so much. I'll check out what I can.

Now I'm wondering if it's working properly now, and the fan kicking on at high speed when I turn the AC on was not proper operation. As a data point, I hauled my 6000 lb trailer over the Santa Cruz mountains last weekend, and I did not have any heating issues. As a matter of fact, it did not heat up even slightly as I had expected it would.

Charlie
 

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If the PCM detects a fault, it runs the FAN at 78% I think as a kind of limp in mode, but you should get a check engine light or other fault status.

If the Fan looses the control signal, I think it runs at 78%. You wouldn't get a fault light.
 

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IIRC there is a separate module (on radiator ) for HD cooling - hoping it trigers a synapse in ColdCase
 

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Big question is this GC optioned with 'MAX COOLING"?
TMI max cooling the PCM supplies a PWM signal to the Cooling Fan Module* - the system can be tested with a scanner, varying the fan speed. There are codes associated SO a scanner may show a DTC, SCANNER not code reader....


* on radiator shroud
 

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IIRC there is a separate module (on radiator ) for HD cooling - hoping it trigers a synapse in ColdCase
The HD fan and SD fan assembly are indeed different. A SD assembly has a what looks like a wire wound resistor like the photo the OP posted. A HD assembly looks like the one below. I think the control module itself is within the motor, but dunno for sure. Its not sold separately. The motor is not sold separately, only comes as the assembly. A 2014 V8 with factory tow definitely has HD cooling. Non factory tow will vary.

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Discussion Starter · #9 ·
Hi. - Thanks for all you info and suggestions.

From what I can tell, things are likely operating they way they should. Yes, I do have the max HD fan/cooling option that comes with the tow package. I can see that at least two of the sensor are working properly, because they show up on the dash display: Engine Coolant Temperature (the guage), and Transmission Oil Temperature (in degrees on the dash display). I checked the sensors themselves to see if there were any loose or corroded wires and found none. The engine runs at normal temperature even when pulling a 6000 lb trailer. That said, I may have the fan system checked out the next time I get them Jeep into the shop.

So, what sent me down this road is the following, which I will take up on a new thread and link below.
I had my oil changed at a Speedee Oil Change service, and immediately afterwords noticed a burning old smell coming into the cabin when stopped (e.g. at a stop light). Apparently the oil filter was "defective" and/or leaking slightly. Speedee Oil Change replaced it and I've been waiting for the burning oil smell to disappear completely. Well, it hasn't even after 150 miles or so, although it's very subtle at this point. There is no visible oil leakage or smoke that I can see, although it does appear to be more on the passenger side of the engine. My thought, which sent me down the defective fan road, was that the fan had somehow changed and wasn't blowing hard enough to clear any engine smell from the passenger air intake. I'll pass on that thought and focus on finding the oil smell.

Here's the new thread. Very Subtle OIl Smell Coming into Cabin

Charlie
 

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Discussion Starter · #10 ·
A final post. Now that the weather has heated up, my fan seems to be operating as before. All looks good for the moment.

Charlie
 
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