my a/c switches to defrost when?

Question

The a/c switches when i go up hill, dodge ram. I suspect a vacuum leak?

Answer 1

You have a bad vacuum check valve. The default position is defrost, so when it looses vacuum that's where it automatically returns to. As is usual on answers, you don't give enough information about the vehicle to get a complete answer. The check valve is located in a vacuum line somewhere under the hood, most likely on the on the passenger side. Go to thedealership and tell them you want the vacuum check valve for the a/c controls. Then find and replace it. It just plugs into the lines.

Answer 2

I not sure it a leak. How many Defrosters and Vents work; They use a flap that the Vacuum can move positions to route the Air to where you select. Just a simple setup. What may have happened, is something came loose and the Flap is Flapping around freely. If, you can look in that area you may see the small rod that the controls connect to. They usually use a small clip and it may have fallen off. Sometimes you find it in the floor and wonder what it is. Sometimes it just lodge somewhere never to be found.
I will try to find some pictures that help you understand what I talk about.
Hard to find a picture. The picture I have not great, but, think of #1 in the picture being the Flap and the direction it positioned it send air where you want. Floor, Middle, Top.
http://www.yourtiredealer.com/corpimages/airconditioning.jpg

Answer 3

swounds like a vaccum leak. check under the dash for all the hoses going to everything till you find the one wherer yyou pull it off and it don't swith to nothing. thats what makes it switch from face to floor to whatever. less you got electronic stuff on the heater box then when you find the one that doesen't switch when you puull it off then it is that cylinoid. get something from the junk yard to be a cheapie the usually work just as good on a wrecked vehicle.

Answer 4

If it was a vacuum leak, would it not happen any time you put the engine under additional load such as when pulling away from a stop? If it's only when going uphill and corrects itself when going downhill, I would suspect that the physical switch is broken and swinging in relation to gravity.

Answer 5

Sorry i did not quite understand...

Do you mean the A/C turns on when you try to defrost the windshield? if so, this is normal... most all vehicles use the A/C "automatically" when the windshield defrost is activated.

Otherwise, might you specify the Question.

Thanks,
"/JOe

Answer 6

this is a normal concern on these vehicles, if it works properly under normal conditions, don't worry about it

Answer 7

you have a bad vaccum check valve or reservoir