I'm not sure if this is a common problem in later model F-150's, but my 2003 XLT is having a strange issue with the a/c that I can't figure out. When the a/c is on and the throttle is pressed down too much, the a/c quickly begins to slow down and soon shuts off. The air can still be heard but it sound as if all of the vents have been blocked and no longer let air pass through. It's very annoying as I travel on the highway a lot and the initial merging onto it and revving up from 30 or 40mph to 60 or 65mph seems to always cuts the air off. But then if I let off the gas, the a/c comes right back on. It seems as if once I reach a certain acceleration/ rpm, all of the a/c vents are blocked. Is this uncommon? And how in the world do I fix it? My first thought was a vacuum leak of some sort but I really have no clue.

Thanks for any help!

 

Its the vacuum line going into The firewall behind the battery on the passenger side of the truck. There is a 3 way valve that the vacuum lines run to right behind the battery on goes into the firewall one comes from the engine and the other idk where it goes but check thoose lines for breaks and leaks the small 1/16 line that goes into the firewall controls your pannel.

 

Sorry for the slow response. Found the three-way you're talking about and sure enough it looks like the guy that owned the truck before me accidentally cut a line that comes in from under the battery and lost the rubber boot that connects the line to the small valve. He wrapped it in duct tape but it was definitely loose so I jammed it back in there and put fresh duct tape tightly around it. I suppose I'll have to look into either replace that whole assembly or seeing if I can find that rubber boot that covers the line into the valve. Thanks for the help!

 

Your welcome bro I replaced mine with a 1/8 size vaccine hose I got from a hardware store. 4' for $1.15 at a hardware store. Good old fashion run of the mill hardware store. Just replace the whole hose with the 1/8" line case the 1/16" hose is impossible to find and taping it just doesn't cut it. Its easy to do once u get the passenger side.

 

Thanks guys! After reading this, I had my truck fixed in 20 minutes. I used a 1/8" drill bit to bore the old vacuum line out of the rubber elbow, forced the line back in and sealed it all with shrink wrap.