Dash HVAC Questions

[77newell]

My 93 coach dash HVAC doesn't work very well and I'm working on getting it up to snuff. So far I've found that the wire cable moved by the temperature control lever had come loose from the lever and I've reinstated it to the proper position. I will not be attacking the AC until next year.

Here are my questions:

1) what turns on the fan nearest the center of the coach that is mounted along with two others in the box in front of the generator fan. No control panel button has caused it to run.

2) what turns on the two fans under the dash. Bi control panel button has caused them to run.

3) since my control panel on the dash doesn't have any air connections to it and yet the dampers in the system are moved by vacuum are there solenoid valves somewhere.

Appreciate any insight anyone has. I've read encantotom's posting and even though his previous coach is a contemporary of mine his was configured differently.