Hi All,

This past Tuesday I dropped my brand new truck at the dealer because no air was coming through the vents but I could hear the blower motor. The problem consists of the AC functioning properly for a period of time and then the air volume slowly fading to nothing out of the vents, but the blower is still functioning. Prior to getting it to the dealer the problem had resolved itself before I could get it in the service department's hands, presumably because whatever had frozen "unfroze". The service department said they checked pressure levels in the AC system and everything was fine and could not replicate the problem. This morning the problem occurred and lasted long enough to get in in the dealers hands so they could see what was going on. They say its a blend door problem, but to me it sounds like the AC is freezing up. The other strange thing was that chilled air would always be coming through the vents even if I had the AC button turned off (when the system was actually blowing air through the vents). In other words, I could not get ambient (warm) temperature air through the vents on an 85 degree day. So does this sound like a situation where the blend door can be the culprit?

 

You just described my issue to a T....i hope you get notifications for this reply..What was the outcome to this issue? it's happened about 6 times to me now and the period between working and not working is getting smaller...Was it a blend issue or AC compressor? Thanks

 

This issue is due to the evaporator core freezing up and turning to a block of ice which blocks airflow. In these designs, ALL air must past through the evaporator core, regardless of any other settings. The short-term measure is to turn off the A/C system and allow the ice to melt, then it will work for a time until it freezes again. Of course, if the clutch is mechanically jammed, then the compressor cannot disengage.

In order to solve, you have to determine why the A/C compressor is not cycling properly and is staying on past the point where it should cycle off. That starts with identifying HOW the system is supposed to work and then determining where the functional breakdown is occurring.

 

Have you or anyone else attempted to add freon to it? In my experience the freon level in the late model AC systems are dammed touchy. Too little and they'll freeze up, too much and they'll distort the compressor body and cause it to wear out VERY rapidly. That's why the manufacturer's now instruct people to empty the system AC completely and then weigh out the replacement Freon charge.

 

My compressor short cycles..Clutch engages for 3-4 seconds then off for about 5 then back on again for 3-4 seconds..I haven't tried adding freon..I never have an instance where warm air is blowing through the vents,i just eventually get a 95% drop in air flow. But that air flow is still cold,just barely coming out of the vents.

 

If your compressor is short-cycling, that is almost ALWAYS a sign that the refrigerant level is too low. There are other potential causes, so don't get fixated on this even though it's the most common reason. The lack of adequate refrigerant can cause the pressure in the evaporator core to drop below freezing due to the lag of the control circuitry which varies with model year, something you didn't provide in your post.

If the evaporator core temp rops below freezing and the incoming air is humid, the moisture in the air condenses on the outside outside of the core like it's supposed to but then freezes into a block of ice. Air cannot travel through a block of ice so airflow is cut off until the ice melts.

BTW, "Freon", a registered trademark of the DuPont company, hasn't been used in Fords for almost 25 years, last being used in the 93-94 span.

 

Thanks for your input,it's helped me realize what exactly is going on.. I live in Florida where its humid almost all the time. I have a 2016 F150 XLT 2.7 ecoboost.. The problem has to be exactly what you are describing because i can go days with out an issue,some times even weeks. At first it seemed if I had my windows down and still had the AC on it would eventually stop blowing through the vents.. Im currently waiting for the next time it stop air flow and check my compressor to make sure the clutch is still engaging.. Thanks again for your input

 

It's under warranty, just take it in and have it checked by the dealership. If you give them a coherent explanation, they will understand what is going on and go down the same path I described. Presumably, they will also have any up-to-date service actions and notices which I wouldn't know about and they should be able to address your concern. If I had to make a SWAG, I'd speculate that they will pull the refrigerant out, discover it's a few ounces light, check for leaks, and then recharge it correctly using their shop equipment.

I'm not up to date on the newest model years since I only do this as a distraction (and to keep my own fleet serviced) and there are always improvements and changes to how functions are done even though the underlying refrigeration theory remains the same.