My 1972 wagon has factory installed A/C. I have had an ongoing issue with the blower switch. The switch has the following positions: Off, Low, Medium, and High. The switch only works on high speed. The switch was replaced a while back and the lower speeds initially worked and then stopped. Where should I start looking for the cause? Today when I had the instrument cluster and radio out, I did a quick check of the wires and didn't see anything obviously disconnected or bare. The second issue is with the two dash vents and the floor vents. No matter where the vent lever is placed, the air only comes out of the defroster vents. I know that the issue is probably a vacuum leak as my 89 Burb had a broken lever clip in the vent box that I had to repair (Cheap plastic that dried in the Florida heat). Again, is there a good place to start checking? Any tips or suggestions would be appreciated.

Thanks for the suggestions Pinto_One! I just checked the vacuum canister hose that runs to the engine. The hose is a tad short and it had worked loose. When I thought about it, I realized that the Pinto was running a bit rough when I pulled it into the garage today. Problem solved! The vents are now working. Checking the blower resistor will be the next step.