AC Compressor Clutch Engaging On Its Own

[JHumphries]

Signature Truck: 2014 Ram 3500 10,000 miles. Outside temp anywhere from 40° to 70°F.
It's happened several times, but tonight I verified the AC Compressor was actually spinning.

Driving along in my automobile... and it starts getting colder. This seems to occur within a few minutes of climbing a hill. The temperature selector has been anywhere from the coldest, but not on Max A/C to mid-way, with AC off every time. The position selector is in Dash vents, and once or twice blended with floor vents, but never anywhere near defrost. If I press the AC button to turn on the AC, wait a second and then turn it back off, the air starts to warm back up.

Tonight when it happened, I stopped in a parking lot and verified the compressor was spinning, (the actual compressor and not just the outer ring of the pulley, i.e. the AC clutch is engaged). I turned on the AC and verified the compressor stayed spinning. I turned the AC off, and the compressor stopped spinning, as suspected. I went through the drive through at Dairy Queen and shut the truck off at the order screen. Halfway home, about 2 miles, I noticed the ventilation was getting cold again. I cycled the AC and the air warmed up.

To summarize, when I go up a hill (unfortunately I can't quantify the hills or angle required to do this.), the AC compressor clutch will engage on its own, until such time as the clutch is told to disengage. I have not knowingly let this go long enough that the compressor clutch would cycle on its own... maybe next time.

Any guesses?

 

[kthaxton]

Weird,
I kind of doubt it's related since yours seems to be more random but....I know on my old 2000 (and I think various other vehicles I've had) the manual states that when the air is set to split between the dash and floor vents, the AC may come on. I don't know why, but that is what it says, and that is what it did. I don't recall if my '15 manual says anything similar or not.

 

[JHumphries]

Weird,
I kind of doubt it's related since yours seems to be more random but....I know on my old 2000 (and I think various other vehicles I've had) the manual states that when the air is set to split between the dash and floor vents, the AC may come on. I don't know why, but that is what it says, and that is what it did. I don't recall if my '15 manual says anything similar or not.

I've never heard that; that's interesting. Most if the time the selector is on full dash though.

 

[LHarper]

Was your defroster on?

 

[JHumphries]

Was your defroster on?

The defroster was not on.

 

[NDanecker]

I have been in line at the drive-thru where I'm directly next to the building and can hear every sound the diesel makes including the a/c clutch and compressor spinning. Similar to the OP with the A/C off, defrost off and Auto Temp selecting not activated I can hear the clutch engage/disengage along with cold and warmer temps via the vents. Oddly though this isn't FULL a/c. For example, if I would set the temp to 69 it wouldn't cool the truck down. Weird to say the least.

It seems there is no way to really disable A/C without shutting the whole ventilation system down (which I haven't tried).

 

[dfb]

Signature Truck: 2014 Ram 3500 10,000 miles. Outside temp anywhere from 40° to 70°F.
It's happened several times, but tonight I verified the AC Compressor was actually spinning.

Driving along in my automobile... and it starts getting colder. This seems to occur within a few minutes of climbing a hill. The temperature selector has been anywhere from the coldest, but not on Max A/C to mid-way, with AC off every time. The position selector is in Dash vents, and once or twice blended with floor vents, but never anywhere near defrost. If I press the AC button to turn on the AC, wait a second and then turn it back off, the air starts to warm back up.

Tonight when it happened, I stopped in a parking lot and verified the compressor was spinning, (the actual compressor and not just the outer ring of the pulley, i.e. the AC clutch is engaged). I turned on the AC and verified the compressor stayed spinning. I turned the AC off, and the compressor stopped spinning, as suspected. I went through the drive through at Dairy Queen and shut the truck off at the order screen. Halfway home, about 2 miles, I noticed the ventilation was getting cold again. I cycled the AC and the air warmed up.

To summarize, when I go up a hill (unfortunately I can't quantify the hills or angle required to do this.), the AC compressor clutch will engage on its own, until such time as the clutch is told to disengage. I have not knowingly let this go long enough that the compressor clutch would cycle on its own... maybe next time.

Any guesses?[/QUOTE
Ac compressor comes on to prevent window fogging...

 

[MJWenrich]

It might be a FCA thing with all their vehicles having the dual temp control deluxe AC system. I say this because I have a rental Jeep Cherokee Limited while my truck is being repaired by the dealer. I was fiddling with the temp control all the way home, driving uphill, about a 75 mile trip. I also noted it blew warmer air going uphill and then cooled off downhill. Now I know what you are thinking but this an auto system that is supposed to account for engine temp change. I don't know if the AC compressor is going on or not but the temp is not constant. I had it in the split level position with no defrost. I was dialing in 70 to 76 degrees to keep warm but not too warm. My Big Horn does not have the dual controls and I have never noticed any change in temp like the OP posted. Just an FYI.

 

[dfb]

It might be a FCA thing with all their vehicles having the dual temp control deluxe AC system. I say this because I have a rental Jeep Cherokee Limited while my truck is being repaired by the dealer. I was fiddling with the temp control all the way home, driving uphill, about a 75 mile trip. I also noted it blew warmer air going uphill and then cooled off downhill. Now I know what you are thinking but this an auto system that is supposed to account for engine temp change. I don't know if the AC compressor is going on or not but the temp is not constant. I had it in the split level position with no defrost. I was dialing in 70 to 76 degrees to keep warm but not too warm. My Big Horn does not have the dual controls and I have never noticed any change in temp like the OP posted. Just an FYI.

When my 92 Dakota did that, I installed a larger vacuum resivoir. This solved the problem..no more ac gong to dash defroster vents.. Straight our ac vents!!