AC changing flow by itself

[Haulero]

I always have my ac set to the front vents, most of the times. Lately I notice that everynow and then my ac switches from front vents to floor/feet vents by itself but it switches back in less than 30 seconds, I'm really worried that eventually, the ac flow will be stuck on floor/feet vents (this happened to a company truck I used to drive) so, does anyone know what the problem is? how to fix it? it may sounds stupid but I noticed the other day that everytime I push the gas pedal hard, ac switches to the floor vents

[PurpleGuy]

Not sure what the problem is but if it makes you feel any better my dad's F150 does it too. It's digital also. It does the exact same thing yours does.

[FordMan77]

Not sure what the problem is but if it makes you feel any better my dad's F150 does it too. It's digital also. It does the exact same thing yours does.

Let me guess, a 2003+ truck? If so I may have a solution for it if you need one

[Haulero]

I just hope that the problem doesn't get worse

[98gtp]

In my car (98 gtp), and my parents car (95 buick regal) the vacuum line going to the climate control was cracked. I replaced mine with a piece of metal brake line along side the transmission selector cable, shortening the line significantly.

The crack in your line must be getting worse because I am running without a vacuum reservoir to my knowledge and the mode does not change on me, even on heavy acceleration. You should fix the line as it is a unmetered vacuum leak with unfiltered air.

[Haulero]

In my car (98 gtp), and my parents car (95 buick regal) the vacuum line going to the climate control was cracked. I replaced mine with a piece of metal brake line along side the transmission selector cable, shortening the line significantly.

The crack in your line must be getting worse because I am running without a vacuum reservoir to my knowledge and the mode does not change on me, even on heavy acceleration. You should fix the line as it is a unmetered vacuum leak with unfiltered air.

Sorry for the question: "the vacuum line going to the climate control...." so this line is behind the climate controls inside the car? I have to take the climate control out and look for it? can you explain a little more. Thank you

[rynoman03]

Its on the Passengers side under the dash foot panel protector that's removeable next to a purple wire. Plug that sucker back in or make sure its snug. Then look for cracks.

[98gtp]

The line is probabally broken near the battery where it enterd the wiring harness.

The vacumme line goes in through the wiring harness on the passangers side, meandering about by the top of the passangers side firewall. I replaced my line from the engine to the controller with a piece of metal brake tubing passing in the cabin beside the automatic shifter cable, in the same gromet, (98 gtp has no reservoir for the vaccume so this turnes a ~8 ft section of vacuume line into ~4 feet) in the cabin it enters the cabin above carpet/ kickboard on passengers side of tunnel. I fished the line through, found its location and slit the foam/ plastic insulation to allow a gradual curve into the climate controller.

I would suggest making a connection within 3 " of the engine side of the vacume lina as otherwise you may twist the fitting off in the car when doing work on the engine (only occured once to me, so have not changed this yet.)

With or without the supercharger you should see a black vacume line entering the wiring harness by the battery on the passangers side, with a long line attached to the engine. (on the supercharger this line attaches beside the brake vacuum line, on the same fitting.)

[Haulero]

The line is probabally broken near the battery where it enterd the wiring harness.

Yes, the line was broke there I fixed it. I hope that stop the problem

[Haulero]

oh man, that sounds like a lot of work, lol may be I need to wait til the weekend

[98gtp]

you could just look for a break in the line in the engine bay, and see if you can fix it there. I tried that first and it lasted a week for me. I believe mine broke in the wiring harness.

I used ~1/8" brake tubing possibly 5/32", it now causes a large vacuum leak when disconnested, but you easily know when something is wrong.