AC only runs when it wants to
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Freshman User
Joined: Oct 2016
Posts: 30
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From: North TX
AC only runs when it wants to
2012 F250 6.2L - AC will be working well with all fan speeds, then airflow just stops and compressor kicks out. Will run (or actually not run) that way for 4-5 minutes, then all of a sudden the compressor kicks in and airflow restarts, and air is nice and cold for another 10 minutes or so when it'll cycle off on its own again.
I've tried all different combinations of AC/MaxAC/fan speeds/and temp settings with no change in behavior. Only occurs in warm weather when AC is on; when just using heat the blower never changes on it's own and everything is great.
Any ideas?
BTW - I've looked through all the HVAC FAQs and probably 200 different threads that come up under different search terms, but haven't seen this particular problem. If it was just lack of cooling but airflow didn't change, then it'd be easy. Or if it was only blower issues in certain speed settings, that's got lots of fixes too. But nothing where cooling and fan quit and restart on their own together that I've found.
I've tried all different combinations of AC/MaxAC/fan speeds/and temp settings with no change in behavior. Only occurs in warm weather when AC is on; when just using heat the blower never changes on it's own and everything is great.
Any ideas?
BTW - I've looked through all the HVAC FAQs and probably 200 different threads that come up under different search terms, but haven't seen this particular problem. If it was just lack of cooling but airflow didn't change, then it'd be easy. Or if it was only blower issues in certain speed settings, that's got lots of fixes too. But nothing where cooling and fan quit and restart on their own together that I've found.
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Freshman User
Joined: Oct 2016
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From: North TX
I have noticed that lately with the weather fairly mild that it will run longer if I keep it in the Max AC setting, but even that will eventually cut out. Pretty much anything over ~80* ambient and I only get a couple of minutes at a time with it running.
One other thing I noticed when I tried to do the clutch air gap check is that I cannot get the compressor clutch to engage when the truck isn't running. Makes it about impossible to get that face bolt loose to check the spacers.
Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
One other thing I noticed when I tried to do the clutch air gap check is that I cannot get the compressor clutch to engage when the truck isn't running.
The gap is set/checked with the clutch de-energized using a set of feeler gauges.
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Lead Driver
Joined: Mar 2006
Posts: 6,259
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From: IL
Blower stops when AC compressor first kicks out. Compressor clutch does engage normally at first, but kicks out after 5-10 minutes and short cycles thereafter. You can sit and watch it engage, disengage, engage on a 30 second cycle until it finally kicks back in and runs after 5 minutes or so.
I have noticed that lately with the weather fairly mild that it will run longer if I keep it in the Max AC setting, but even that will eventually cut out. Pretty much anything over ~80* ambient and I only get a couple of minutes at a time with it running.
One other thing I noticed when I tried to do the clutch air gap check is that I cannot get the compressor clutch to engage when the truck isn't running. Makes it about impossible to get that face bolt loose to check the spacers.
I have noticed that lately with the weather fairly mild that it will run longer if I keep it in the Max AC setting, but even that will eventually cut out. Pretty much anything over ~80* ambient and I only get a couple of minutes at a time with it running.
One other thing I noticed when I tried to do the clutch air gap check is that I cannot get the compressor clutch to engage when the truck isn't running. Makes it about impossible to get that face bolt loose to check the spacers.
Turn your ignition to the on position, while in AC mode, this should make the clutch engage so you can loosen the bolt. Once the bolt is loose, then turn the ignition off.
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Thread Starter
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Freshman User
Joined: Oct 2016
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From: North TX
I know my gap is slightly too large, so wanted to remove a spacer or two to get it back in spec. To lock the clutch for removal of the center bolt, I need to engage it. All the videos and write-ups just talk about taking the ignition to the RUN position with AC selected and it should engage. Mine doesn't unless I start the truck.
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Freshman User
Joined: Oct 2016
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From: North TX
Tried that procedure and my clutch won't engage unless the truck is actually running.
Fleet Mechanic
Joined: Nov 2016
Posts: 1,343
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I think the fan is the key here. Years ago I had a car that developed these symptoms. Fan only worked on speeds 3-4. Settings 1-2 gave no fan output. HVAC compressor would only engage when fan set to 1-2 (no blower). Turn fan to setting 3 or 4, blower kicked in but compressor shut off.
This was caused by a short in the fan's resistor block triggering the HVAC to shut down like the air was turned off.
Somehow the fan turning off is signaling the a/c to shut off.
This was caused by a short in the fan's resistor block triggering the HVAC to shut down like the air was turned off.
Somehow the fan turning off is signaling the a/c to shut off.
Thread Starter
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Freshman User
Joined: Oct 2016
Posts: 30
Likes: 0
From: North TX
I think the fan is the key here. Years ago I had a car that developed these symptoms. Fan only worked on speeds 3-4. Settings 1-2 gave no fan output. HVAC compressor would only engage when fan set to 1-2 (no blower). Turn fan to setting 3 or 4, blower kicked in but compressor shut off.
This was caused by a short in the fan's resistor block triggering the HVAC to shut down like the air was turned off.
Somehow the fan turning off is signaling the a/c to shut off.
This was caused by a short in the fan's resistor block triggering the HVAC to shut down like the air was turned off.
Somehow the fan turning off is signaling the a/c to shut off.
Anyone have a circuit diagram handy? Would like to see just how the different switches interact to troubleshoot in a more coherent manner than I am now.
Fleet Owner
Joined: Apr 2008
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From: 0,0,1
I don't think that works because the clutch draws too much current and would drain the battery. As a safety feature the engine has to be running in order for the clutch to be able to engage.
Fleet Owner
Joined: Apr 2008
Posts: 24,319
Likes: 5,128
From: 0,0,1
Got a strap wrench?