I have a good understanding of how the ac system operates in general. I was wanting to see if anyone can offer a breakdown of how the vent system works.

I have a 91 ford ranger that blows fairly cold after the 134 upgrade. I was experiencing very low airflow at the dash vents so I double checked and repaired the blower motor connection which was loose. After pulling the blower motor and resistor switch for inspection, I rinsed the evaporator core of what little debris I could find and put it all back together (I have since ordered a can of cleaning foam and will be using that and cleaning the evaporator again to be sure it's clean for proper airflow). The small vacuum line coming from the front of the plastic reservoir broke off and I can't find where it's routed to repair the existing line. I noticed very low airflow still at the vents. I checked the vacuum motor behind the glove box and found no vacuum at the white vacuum line that feeds it. I ran a new vacuum line from the reservoir through the fender and connected it to the vacuum on that vacuum motor which is now working I assume. This is where my confusion lies as I don't have a clear understanding of what should be going on under the dash.

When the vehicle starts (AC on or off makes no difference), that vacuum motor actuates and pulls the lever in which I believe opens or closes the fresh air/ recirculated air door? After repairing that vacuum line there was a noticeable increase in airflow at the dash vents. All vent positions work as they should(vent, defrost, floor blow in the proper location when selecting the appropriate position). After reviewing several diagrams, I'm thinking there should be a check valve in line between the reservoir and the vacuum motor? Im used to feeling a noticeable difference when selecting between normal ac and max. Im also used to hearing that air selector door open and close when selecting between the two but I see no noticeable difference between norm and max in terms of airflow or temperature. When switching between normal and max I also see nothing happen at the vacuum motor which I thought should open or close the fresh/recirculate door. If anyone could offer an explanation of that system I'd appreciate the help. Im also listing my specific questions below.

1. Do I need a one way check valve in line?
2. If that is the actuator vacuum motor for fresh air which position, up or down, is open or closed?
3. Where are the air intake inlets for fresh and recirculated air?
4. Where is the white vacuum line from the vacuum motor routed through? I have temporarily routed one through the fender but it runs through the door jam and could eventually fail due to wear or could get pinched.


thank you for any assistance