"69 Cutlass. AC is blowing warm air on passenger side. Drive on long trips in the summer. Still R12. AC isn't great but 10-15 degrees warmer on passenger side. Added manual shut off valve to heater supply hose. Looking for suggestions before tearing into the duct work to check valves, doors etc. Wife needs cooler air.

 

I ASSUME you are talking about the air blowing through the dash vents. There is only one temperature blend door that controls the air to all the vents. Similarly, there is only one plenum that feeds all the vents. If the temp is that different, check for thinks like a damaged or disconnected flex duct between the plenum and the dash vent. There is no individual temperature control features that would cause differences in side-to-side temperatures.

 

Thanks Joe, Kinda what I thought but surprised by the difference in the two ducts. Middle close to driver's side temp. Passenger side seems to have the same air flow but significantly warmer. Possibly getting some warm, outside air mixing with the cold air. Maybe nearer the right side so more noticeable there. Seems the same on recirculate as well as normal so that door may not closing all the way or not sealing well. Rubber around the edge is 50 years old so.... Even though pressures etc. seem good, air really isn't as cold as it should be with R12 so maybe effecting all three vents and just more noticeable in the right side. Appreciate your help.