AC switching to defroster on it's own.

I have a 98 explorer that has been doing something odd for a little
while. When the engine RPM goes up as the vehicle is going up-hill
the AC stops coming through the vents and switches to the defroster on
it's own.

I don't know much about cars, but if someone would like to walk me
through troubleshooting/fixing this I would appreciate it.


TIA

wrote:
> I have a 98 explorer that has been doing something odd for a little
> while. When the engine RPM goes up as the vehicle is going up-hill
> the AC stops coming through the vents and switches to the defroster on
> it's own.
>
> I don't know much about cars, but if someone would like to walk me
> through troubleshooting/fixing this I would appreciate it.
>
>
> TIA
>

You have a vacuum leak somewhere between the intake manifold and the
flow selector. I found mine coming from one of the 4 wheel drive front
axle lock vacuum solenoids. There is usually a red line that crosses to
the passenger side and then hits a vacuum canister (ball). From there a
line feeds into the cabin to hit the manifold behind the glove box.

Steve Sigman wrote:
> wrote:
>
> You have a vacuum leak somewhere between the intake manifold and the
> flow selector. I found mine coming from one of the 4 wheel drive front
> axle lock vacuum solenoids. There is usually a red line that crosses to
> the passenger side and then hits a vacuum canister (ball). From there a
> line feeds into the cabin to hit the manifold behind the glove box.

I agree, vacuum problem. On my 99 when I purchased it new, it did the
same thing. Turned out there were 2 vacuum lines in the engine
compartment ( passengers side, by the alternator) that were never
hooked up at the factory. Once the service guy hooked them together, it
solved the problem. You might want to look there also.