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Cooling fan is not engaging can we fix it?

Tiny
FRANCISJANSEN
  • MEMBER
  • 2007 DODGE RAM
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 341,000 MILES
Cooling fan is not engaging can we fix it?
Tuesday, July 7th, 2020 AT 12:25 PM

12 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

Does the A/C work? If it does. can you give me the high and low pressure readings?

The radiator cooling fan should come on at 208 degrees and go off at 180.

https://www.2carpros.com/articles/how-an-electric-cooling-fan-works

I attached a wiring diagram for you to view. You need a test light or voltmeter to do some tests.

https://www.2carpros.com/articles/how-to-check-wiring

Roy

OPERATION

The A/C condenser fan used in gasoline engine equipped models (except SRT 10) is controlled by the powertrain control module (PCM). When the A/C-heater control is set to any A/C position, it sends a request signal on the CAN-B bus to the totally integrated power module (TIPM), which then transfers the request on the CAN-C Bus to the PCM/ECM, which sends a signal on a dedicated hard-wired circuit to the totally integrated power module (TIPM) to energize the internal A/C condenser fan high side driver. When energized, the A/C condenser fan high side driver provides battery current to the condenser fan motor.

The A/C condenser fan control system is diagnosed using a scan tool.

The components of the A/C condenser fan cannot be adjusted or repaired and must be replaced as an assembly if found inoperative or damaged.

Radiator cooling fan clutch

A thermostatic bimetallic spring coil is located on the front face of the viscous fan drive unit (a typical viscous unit is shown in. This spring coil reacts to the temperature of the radiator discharge air. It engages the viscous fan drive for higher fan speed if the air temperature from the radiator rises above a certain point. Until additional engine cooling is necessary, the fan will remain at a reduced rpm regardless of engine speed.

Only when sufficient heat is present, will the viscous fan drive engage. This is when the air flowing through the radiator core causes a reaction to the bimetallic coil. It then increases fan speed to provide the necessary additional engine cooling.

Once the engine has cooled, the radiator discharge temperature will drop. The bimetallic coil again reacts and the fan speed is reduced to the previous disengaged speed.
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Tuesday, July 7th, 2020 AT 12:47 PM
Tiny
DAMANDE
  • MEMBER
  • 1 POST
  • 2006 DODGE RAM
  • 5.9L
  • 6 CYL
  • TURBO
  • 4WD
  • MANUAL
  • 173,000 MILES
2006 Dodge Ram 3500 ST. 5.9L diesel. 4WD, 6 speed. Had it to firestone and C Classic Dodge up around my area. The A/C is acting up so replaced the condesor, accumulater, and compressor with all new seals. Firestone couldnt do anything because there was sealant in the a/c and according to him his machines couldnt handle that because it would clog it. So he suggested an actual dodge dealer. So the next week set up an appt with C Classic Dodge in Clearfield, PA. They told me that the a/c isnt working because my engine fan is faulty and that the plug in the harness was tapped up and tucked into the bottom of the engine somewhere. So he tells me that since that fan is spinning fast enough it isnt cooling the a/c condensor enough which is causing my a/c to not work. I know a little bit about trucks and such. Learning a lot about diesels just by having one. I learn from experience and a lot of research from different sources. But never had to mess with the fan on any of my vehicles. So with my fathers help he figured that the fan clutch system that is on it now is just a manual one with no electric to it. You could see the fan and whole clutch motor spinning and C Classic was trying to tell my father it was electric and he replied how can it be electric when its spinning? So then they tell him that it is the wrong thing. Why couldnt they have told me that in the first place. Regardless, so here is where I am at. So what I need is a picture or schematic on what this bracket looks like that holds the electric fan clutch and what the fan clutch and fan look like so I have a better idea on what im ordering. And in fact this is the problem, would that affect the a/c like C Classic was saying? I have a feeling that the guy where I bought my truck from either switched the electric one out to sell or bought or used another manual one because it was cheaper. Thank you for your time. Matt
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Thursday, May 13th, 2021 AT 12:13 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
What would happen with your air if no fan cooling is that you would get cooling for a while then it would stop. Your fan on your truck is electronically controlled and should lock up as temp gets warm or if pcm calls for it. There is a fuse and am sending the pic of where to check for it. What the guy was probably trying to explain is that maybe the harness is broken under the engine hard to tell. See pics for fuse and other pic is of fan controller.
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Thursday, May 13th, 2021 AT 12:13 PM (Merged)
Tiny
UNDER THE SHADE TREE
  • MEMBER
  • 4 POSTS
  • 2006 DODGE RAM
  • 5.9L
  • 6 CYL
  • TURBO
  • 2WD
  • MANUAL
  • 276,000 MILES
Throws code for fan clutch. Replaced fan clutch. Fan clutch kicked on initially, but is still not kicking on like it should. Thanks for your time, any help is appreciated!
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Thursday, May 13th, 2021 AT 12:13 PM (Merged)
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Hi,

What is the code that you are getting? Is it P0480? Is it just one or are there more? Please provide all of them if possible.

If it is the P0480 then here is the diagram for this. If there is another one, I can send that as well.

I doubt you are in limp in but it is possible if you have a greater ECM issue. Do you notice if the engine is getting hot? If the temperature is rising this would be more likely to explain your driveability issues. The ECM is degrading the engine to keep it from overheating. If this is the case, fixing the fan issue should resolve everything.

Let me know and we can go from there. Thanks
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Thursday, May 13th, 2021 AT 12:13 PM (Merged)
Tiny
UNDER THE SHADE TREE
  • MEMBER
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It set a soft code P0483 fan speed. New Fass lift pump was installed last Friday dummy meter read 19-20 mpg empty no load highway. Hooked up to my trailer and I lost mpgs and power. That's when I scanned it and found the soft P0483.
It fan was running lightly this morning after start up maybe not my problem. I'm in South Texas so the thermostat is a 185 new radiator nine months ago. Pulling large hills in hill country with a slide in camper and cargo trailer yesterday temperatures were up to 190-195 and the fan was not noticeably roaring?
What temperature does the fan clutch engage?
Maybe not my problem?
I will check the wiring harness this evening and get back to you.
My main issue is 8 - 9 mpg and loss of power.
I don't know if my Bluedriver scanner clears the code or just hides it from me? Maybe the ECM is still protecting itself?
Thanks for your time.
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Thursday, May 13th, 2021 AT 12:13 PM (Merged)
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
The fan is duty cycled so it will not be roaring unless it needs to. The fact that it is running at a high of 195 degrees, I would not worry about this. As for the poor fuel mileage and loss of power, can you monitor your actual vs desired fuel pressure with your scan tool? This sounds like a fuel control issue but this information will help with that. Sometimes the high pressure pump is the issue but more than likely it is the fuel control actuator or lift pump. If the ECM is commanding higher pressure then what it is actually doing, this is either the FCA is not allowing the fuel into the high pressure chambers or the lift pump is not supply enough fuel to achieve the pressure. Usually, there are no DTC's with this issue in the model year. The fact that you have replaced the lift pump, I would look at the control actuator is the commanded pressure does not match the actual or at least close. It should be with 100-150 PSI.
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Thursday, May 13th, 2021 AT 12:13 PM (Merged)
Tiny
UNDER THE SHADE TREE
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I had made a return post but it seems to have disappeared.
I forgot to mention to you and the shop the truck was just in.
When truck is cold (morning start or after sitting) if I rev the motor rpm's stall at 1,500 rpm's, let off throttle, throttle back up and they will rise as high as demand with a slight jerk/noise like something kicks in again around 1,500 rpm's? It is hard to explain?
It is a standard six speed. So I guess I don't notice it if I just start mashing gears?
Fca?
The mechanic said my injection pump was good? Did he check actual pressure vs demanded?
I can only see actual fuel pressure, I assume the reading is from the rail pressure sensor. (6800-7300psi at idle)
I did do test the fca default by unplugging it fuel pressure jumped to maximum 26000 something psi, in 22 seconds it dropped back to normal idle pressure. I understand that this isn't a true test of the Fca.
What bugs me is.
Before injectors 19- 20 mpg
After injectors 15 mpg
Before new lift pump 15mpg.
After new lift pump 19-20mpg
Monday tow 11.7 mpg & throw soft fan clutch code
Replace fan clutch still 15mpg
The mpgs are off the dummy meter / overhead. I have hand calculated and its 2- 2.5 less.
Thanks for your time.
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Thursday, May 13th, 2021 AT 12:13 PM (Merged)
Tiny
UNDER THE SHADE TREE
  • MEMBER
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New FCA.
I won't really be able to tell if it helped at all until tomorrow.
All the sensors readings look the same.
Watching the fuel rail data from Horse Shoe Bay to Austin ( hill country).
My rail pressure doesn't want to break 20,000 psi?
If I would dig into it pedal to the floor going up hill the max it pressure it ran up to was 20,500 something then it would drop to 18,000 to 15,000 while pedal is still to the floor?
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Thursday, May 13th, 2021 AT 12:13 PM (Merged)
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Okay. It is harder to tell if these fuel pressures are correct without knowing what the PCM is commanding. The fact that it is building pressure that high is a good sign. That shows that it has enough fuel volume (lift pump is working) to build the pressure and that the high pressure pump is able to supply the rail with that amount.

Again, what we don't know is if that amount is what it is supposed to be doing. With WOT you should be getting close to max PSI which would be about 26,000 PSI and the fact that it is dropping with the pedal still to the floor is concerning. However, it could be okay if the load is dropping, then it won't need max pressure.

A drop in fuel mileage would be expected when towing but the fact that you are throwing that code is a little odd. Does it only throw the fan clutch code when you are towing?
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Thursday, May 13th, 2021 AT 12:13 PM (Merged)
Tiny
MICHAELMUNNS
  • MEMBER
  • 2 POSTS
2005 dodge 2500 diesel. I have a similar problem fan clutch went out replaced and it kicked on but then went out again on the first drive after about 15 minutes of interstate driving. Let sit for about 2 hours and cranked up and fan was on and moving some air, sounded like it was on about 50% just at idle. Moved the truck and cranked it multiple times fan was on every time, took a 15 min drive and fan was working initially, got to next stop to pick up trailer and fan was not working any longer. Any help would be greatly appreciated.
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Sunday, May 26th, 2024 AT 9:47 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
I have seen the cooling fan relay go out and cause this problem.

here is a video to help you swap it out:

https://youtu.be/_wyb8rr6EWI?si=A5v0J4bUiw-2k8vz

Please go over this guide and get back to us.
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Monday, May 27th, 2024 AT 9:55 AM

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