Climate Controls not switching

[s_firestone]

Hello, I recently acquired a 1991 Dodge Ram B250 Van. The climate controls do not switch vents when actuated. What is the most common cause of this on these old vacuum actuated vents? My first inclination is to order the A/C-Heat Selector Switch.

Is there an electrically powered vacuum pump or do the climate controls operate off of the manifold vacuum?

The van has the dual AC unit.

On a related problem I am replacing the Blower switch as the fan speed only blows on low. The switch PCB back is discolored due to heat and gives erratic reading on a multimeter. I will likely inspect/replace the resistor at the same time.

I hope to have a service manual soon...

Thanks in advance,
Stephen Firestone

[s_firestone]

Answering my own question... Lightly tugged on each of the under hood vacuum lines. Vents started switching. Likely a dry rubber connection, will put a little silicone grease on the connections.

[Dodgevanman]

BTW, the blower motor resistor is behind the glove box. The glove box pops out.

[s_firestone]

Thanks! I spent about an hour vacuuming leaves out of the blower motor. I suspect thats what did in the switch and/or resistor. The vehicle must have sat at some point with the window down or the door open(The only inlet I can find is at the passenger seat footrest), or something was nesting. There were enough leaves to almost completely fill the space between the evaporator and blower housing.

[Chump]

Another common vacuum leak area is the short vacuum harness that attaches to the back of the dash switch. It's about a foot long and the rubber ends fall apart.

[Dodgevanman]

Chump...you got that one right. I was helping my father in law with his '85 B250..while we changing the blower switch, that stupid connector disintegrated. Luckily we were able to find a good one at a junkyard.