'93 Caravan 3.0 A/C works on high, not on low?

I have a '93 Caravan 3.0L that is one fickle b*tch. The a/c and heater both
blow when switched to high but not at low. When you switch it to low you
can hear the compressor kick in but there's nothing coming through the
vents. Also, under acceleration, air comes through the defroster vents
instead of the vents it's supposed to come through--occassionally. If
anyone knows how to fix either of these problems, please help! Thanks!

Carla

 

Replace the Blower Motor Resistor Pack (about $12 for part at dealer).
It is located under the hood on the right side firewall. Has a five-way
connector (usually white) plugged onto it. If your connector is cracked,
burned or brittle get the kit.

 

As BG said, replace the blower motor resistor to get your low speed
back. The same thing happened to my '95 Dakota last December - the
connectors corroded, overheated and melted the body to boot.

The airflow is changing vents under acceleration because the engine
intake manifold vacuum drops when you open the throttle. The heater
doors are all run by vacuum actuators with spring return, so when
the vacuum drops they change position. It will be more noticeable
in heavy acceleration, like highway on-ramps, than in light
acceleration, like city traffic. After 10 years, your Caravan may
have a cracked and leaky vacuum hose or accumulator.

Mike