I am restoring a 1970 280SL and have completely disassembled the heating unit. As many have commented, the airflow from the Behr blower is lacking. I work at SPAL, an Italian maker of fans and blowers, and asked our tech department to see what they could do. Because we don't offer a blower motor as a bolt-in replacement, the tech wizards took a blower motor (model A45) from a standard SPAL blower, and retrofitted it into the Behr unit. It required drilling holes in the motor housing for the two horizontal bolts that hold it in place and affixing a 3 speed resistor to reduce current draw for the car's existing electrical system.
The resistor is 3 speeds, but only low and medium are hooked up, which seems to offer plenty of airflow over the standard. However, I have yet to install it in the vehicle. Attached are a couple pictures of the before and after. You will see that the resistor is placed near the blower wheel to offer adequate airflow.
Hope you find it interesting!
Cheers,
Tom
