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Hammer Time
Hammer Time, L1 Master Technician
Category: Car
Satisfied Customers: 4942
Experience:  ASE Mastertech with Adv level Engine performance cert.
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1994 Dodge caravan: air flow to defroster vents..vacuum..wipers

Customer Question

1994 Dodge caravan AC blower will switch air flow to defroster vents upon acceleration. You can then let off gas move blower switch back to low and when you here door/flap open or close, which ever it does you can then move blower switch back to high and it will discharge air flow from dash vents again until moderate accelration is applied and it will return to defrost vents. This appears to be some kind of vacuum problem like the old vacuum wipers. If so where is the vacuum motor, switch or block that should be checked? I sure can't find it.       Thanks, XXXXX XXXXX Phoenix
Submitted: 11 years ago.
Category: Car
Expert:  Hammer Time replied 11 years ago.
Those mode doors are vacuum operated. Defrost is the default position in thhe absense of vacuum. Your problem is you have a vacuum supply issue. Look under the hood and there will be a small plastic tube coming through the firewall either near the heater hoses or the A/C pipes. Follow this hose to it's source and make sure it's connected. Look the hose over real good for cracks, chaffs or leaks. If there are any other hoses branching off of it, follow them also as the often use a vacuum resevoir tank to store vacuum. any leaks there will do the same thing. If nothing is found under the hood, start tracing the hose into the passenger compartment and look for problems there.

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