Vintage Cars: 1978 280CE Heating problem, 280ce, hose connections

Question

DSCF4621 Hi Ron,
I have some heat! The heat through the defrost is a lot hotter than the heat through the main vents. I achieved this by by-passing one of the hose connections on the main a/c (see photo)which would seem to indicate that the main control is malfunctioning, is this repairable?
Michael

Answer
great , when you told me you bypassed the lines , did you not do it to the two lines in and two lines out of that servo ?  The servo is the big black box on the top of the photo. Or did I misunderstand?  THe round thing is the auxillary water pump which moves coolant to the heater core  when car is at idle.
both  the Servo and aux water pump are not repairable, and often fail.  They can be bypassed , but your vents will not work but you will get heat