Heater doesn't get warm enough
 

1992 300-E M-103 40,000 miles block & radiator have been drained twice every couple of years. With heater control wheel to full and car warmed up I am geeting heat at the front defroster vents and some at the two end vents for passenger and driver.
It seems like a blockage may be causing not all the heat to reach the passenger compartment.
Any recommendations would be welcomed.

Bob Geco
1992 300-E

If you disconnect the wires to the heater valve you should get full heat. IF not, either the valve is stuck partially shut or the heater core is plugged.

Also check the auxilary circulator pump..