1991 300SEL HVAC Problems
 

Hey, first post here, and I've got a problem with my (dad's) car.

The heating system started screwing up recently, so we sent in and received a rebuilt HVAC control, but still had some problems. Previously, the vehicle was not blowing hot air AT ALL, but after replacing the control and a fuse, we have run into a brand new issue.

When we hit the defroster, the recirc button light would light up and flash, and the system would blow cold/outside temp air on high. No other buttons that we could press would fix anything, it stayed like that until the car was turned off.

Has anyone else had a similar problem to this? Any insight or tips would be appreciated.