A/C Always Running w/ Fan On....... Why?

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Frank Wine

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Hello, my 2014 Ram 5.7 V8 seems to have an issue with the A/C clutch engaged whenever the fan system is operating in the car. Regardless of whether the A/C button is on or off in the vehicle, the clutch is running and blowing A/C cold air through the vents. Note that this is occurring when not in defrost mode and I'm not running on Auto climate control.

If I remove the fuse for the A/C Clutch Relay (F62), the A/C stops running as expected an normal vent air will blow. I have already taken to the dealer and they have said my system is operating as designed but I have no way to just have the system push non A/C air through the interior without removing the F62 fuse, so I can't believe it's working as designed.

Has anyone else run into the same issue? Any advice on where to look next?
 

Danes

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I’d say first off, find a different shop. Both my ‘13 and ‘19 Rams with the 5.7 will definitely blow normal, not-cooled “vent” air through the vent system with or without the fans on. If you have to pull the fuse to get the compressor clutch to dis-engage, that is not normal operation at all, and I venture a guess that there is probably a short in one of the fan or a/c relays causing this issue.


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Frank Wine

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Thanks for the help, I had taken my truck to the certified Ram dealer where I purchased it. I found it very hard to believe as well.
 

Danes

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The only reason I take mine to the dealer is because it’s my only option where I’m at.....hopefully with my next move, I can find a decent shop.


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Ricks Ram

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Thanks for the help, I had taken my truck to the certified Ram dealer where I purchased it. I found it very hard to believe as well.
The ATC will keep the compressor engaged at all times when it's on. When you take it off of ATC and run it on manual vent with the A/C off the compressor should disengage. If it doesn't there is most likely some type of issue. Many of us upgraded our trucks to ATC and noticed that our compressors were running at all times whenever we had it on any setting. We eventually figured out that we needed to install the Humidity Sensor that mounts to the right of the rear view mirror. The compressor will stay on by default if it doesn't detect the sensor. I have seen several cases where the sensor had been removed when a windshield was replace and the sensor was left disconnected or completely left off. Not knowing if you bought your truck new or not these are the things it may be. If you bought it used it may have been upgraded by someone else who didn't install the Humidity Sensor. If the truck came with ATC there is a possibility the windshield was replaced and the sensor was left disconnected or completely gone. Check and see if the sensor is correctly mounted to the and connected. If all that checks out it could be a bad sensor or other issue. If the compressor continually runs there should be DTC codes (Diagnostic Trouble Codes) stored in the HVAC module that the dealer can retrieve to try to narrow down your issue. I personally don't let anyone touch my truck, especially a dealer. We have some smart techs on this forum but unfortunately they don't work at any of the dealers around hear. I tested several factory ATC trucks when we were trying to figure out why the compressor was continually on in our upgraded trucks and the compressor disengaged on all of them when I put then on manual vent fresh air. You can take it to a qualified shop that has the equipment to check for DTC codes or you can purchase the Alfa tool and run diagnostics yourself. This is what many people including myself do. I personally take my truck off ATC and run vent as often as possible to avoid the wear and tear on the compressor. With all that being said the ATC trucks do have strange quirks and a mind of their own so you never know. I can say 100% my truck with added ATC and my buddies 17 Bighorn with factory ATC act identical now and both compressors disengage when the truck is on vent.

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Frank Wine

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Thanks for the insight and detail. I confirmed that the humidity sensor is completely intact and connected but realize it could still be faulty. It looks like I can purchase a replacement for $55 but would like to know this is my solution before purchasing a sensor that I may not need. I actually never run my truck on Auto Temp Control to save wear on the compressor (like previously mentioned).

Is there anyway to know if the humidity sensor is bad?
 

Ricks Ram

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Thanks for the insight and detail. I confirmed that the humidity sensor is completely intact and connected but realize it could still be faulty. It looks like I can purchase a replacement for $55 but would like to know this is my solution before purchasing a sensor that I may not need. I actually never run my truck on Auto Temp Control to save wear on the compressor (like previously mentioned).

Is there anyway to know if the humidity sensor is bad?
The only thing I would suggest is checking the truck and the HVAC module for any DTC codes. You would think the dealer you took it too would have done it but who knows? In a case like this you don't want to just throw parts at it hoping to fix it. The main components of the system are the HVAC module, heater control bezel, Humidity Sensor and the Interior Temperature Sensor for the ATC system located under the ignition by your right knee plus of courseall of the wiring and connectors. I would be very surprised if had anything to do with the temp sensor. Most people never pay attention to whether or not the A/C compressor is engaged so this may be a more common issue that we realize. It took us almost a year to notice it after we upgraded our trucks to ATC and may have never picked up on it if one of the guys didn't have to replace his compressor and happened to notice it was on all the time. If you have the Alfa tool you can check the truck for DTC's or you can take it to a shop that has the correct equipment to scan your truck.

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Frank Wine

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Thanks, all. I went ahead and ordered a new humdity sensor, installed, and the problem is solved!! The system works as designed now and the A/C compressor only runs with the A/C turned on or with ATC engaged. Thanks for the help and really appreciate this forum!
 

Ricks Ram

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Thanks, all. I went ahead and ordered a new humdity sensor, installed, and the problem is solved!! The system works as designed now and the A/C compressor only runs with the A/C turned on or with ATC engaged. Thanks for the help and really appreciate this forum!
Glad to hear you got it figured out. Isn't it funny that the dealer said it's normal behavior for the compressor to stay on??? Had you not taken it upon yourself to do your own investigating you would have just assumed they were correct. It really irritates me when dealers give incorrect information just because they don't want to deal with it. All they would have had to do is check the truck for DTC codes and it should have told them what the problem was.

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