Two summers back, I replaced the fan motor and heater core on my 240 sedan -- I remain convinced that Volvo built the car by suspending the heater system in space somehow, then building the car around it -- and I am now getting really strange behavior from the heater. When the heater (cool-hot) control is OFF, the right dash vents are blowing warm air while the left ones blow cool air. Anyone have any theories as to why this should be happening? Any help would be appreciated.