Heating And Ac On At Same Time
 

I replaced the expansion valve and dryer and recharged the system with R12. It is working perfect. When the control is on full heat, the compressor is on and running. There is cold air being delivered to the back seat vent and hot air to the front vents. When in max cooling mode all vents (center vents excluded, probably bad) deliver cold air. The only pod that I know is good, is the one at the driver side kick panel. It will stay operated with a mighty vac connected to it. I have been looking at the posts concerning w126 vaccuum pods and have not seen anything describing heat and air on at same time. Could this be a climate controller unit problem? I will keep searching the archives. I hope someone can take a short cut to the trouble. Car is a 1989 560sel. Thanks

Unless you choose the EC button the compressor will run no matter what the temperature is that you select. One of the points for doing this is to be able to obtain dehumidified air even when it is being heated.

normal action of the climate controller will shut the center ducts when the temp chosen has warm air being distributed.

By the way, the rear vent will supply only fresh air OR a/c!

There are heater ducts under each of the front seats for HEAT to the rear.

No air conditioned air to the backseat, MBDoc?

There is no cold air from center vents when the system is set to max cooling. From reading the archives, I think I am in for more for more work. Thanks Topgun