ac "odd" behavior?

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Just Another - 14 Jul 2006 00:11 GMT

... but I've been surprised what "normal" is before.

I have a '97 Ram Van B2500, standard AC (front only). Under idle or
cruising conditions, all is fine & ac comes through the dashboard fairly
strong (might need recharge).

Under acceleration or hillclimbing load, the ac comes through the lower
(heater?) vents. When I back off on the throttle, the ac again comes
through the dashboard. When the ac's coming through the lower vents,
nothing comes out the dashboard.

So, is this normal behavior? If not, what would cause it? I know that
the heater/ac are a single black-box unit, but my Haynes manual doesn't
describe it very well.

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Max Dodge - 14 Jul 2006 05:04 GMT

Vent position (floor, panel, defroster) depends on a set of vacuum actuated
doors. Under hard acceleration, vaccum changes, and thus so does the
direction the A/C blows.

This is normal.

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Max

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> ... but I've been surprised what "normal" is before.
>
[quoted text clipped - 10 lines]
> the heater/ac are a single black-box unit, but my Haynes manual doesn't
> describe it very well.

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Just Another - 14 Jul 2006 05:42 GMT

> Vent position (floor, panel, defroster) depends on a set of vacuum actuated
> doors. Under hard acceleration, vaccum changes, and thus so does the
> direction the A/C blows.
>
> This is normal.

Thanks. It'll probably be less annoying after I recharge the ac.

> > ... but I've been surprised what "normal" is before.
> >
[quoted text clipped - 10 lines]
> > the heater/ac are a single black-box unit, but my Haynes manual doesn't
> > describe it very well.

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RamMan@dodgecity.cc - 14 Jul 2006 13:35 GMT

>Vent position (floor, panel, defroster) depends on a set of vacuum actuated
>doors. Under hard acceleration, vaccum changes, and thus so does the
>direction the A/C blows.

>This is normal.

True, this is how the vents work, but my bet is if you've had this vehicle
for a while that this is possibly "not" normal behavior to you else you
wouldn't be asking about it now after so many years of ownership.

It hasn't always done this, right?

My own guess is you've developed a vacuum leak, possibly due to a broken
vacuum line somewhere. Just "where" would be anyone's guess, but one of
the more common places is right at the top of your cruise control vacuum
cannister. If your vehicle has 'cruise' does it still work? If not, then
you've found your leak. Fix the leak (replace the line) and you will have
fixed your cruise and your AC. ;-)

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TBone - 16 Jul 2006 22:03 GMT

That is complete bullshit and does not indicate normal behavior. Do you
think that the engineers did not take the vacuum drop typical with hard load
or acceleration into account when they designed it? What this does
indicate is either a defective check valve (used to prevent those vacuum
changes from effecting air flow) or a vacuum leak after it.

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> Vent position (floor, panel, defroster) depends on a set of vacuum

actuated

> doors. Under hard acceleration, vaccum changes, and thus so does the
> direction the A/C blows.
[quoted text clipped - 15 lines]
> > the heater/ac are a single black-box unit, but my Haynes manual doesn't
> > describe it very well.

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