[s-cars] Heat on all the time?

[Beer, Jerald S.]

Mike
  There may be a couple of problems. First, get some gauges. You don't
want to overcharge, it can do plenty of damage. I think the low side
should be around 30-40 psi, don't remember high side exactly, but maybe
in the 120 range (I am sure someone here can help). If you have too
little refrigerant, the compressor won't turn. If you were able to add a
can, you weren't below that minimum, so be careful adding another can. 
One of the problems is the design (at least on my Cabriolets and my 91
200qa). The hot water is always circulating through the heater core. If
the water is not completely blocked off, you get heat with your AC. Just
for grins, try blocking the heater core so no hot water flows in (I
believe the hoses are under the plenum on the firewall, but don't
remember). You won't have heat obviously, but you can help isolate the
problem. 
Regards,
Jerry
91 200qa
 
Just drove ~500 miles this weekend with no AC, and the heat partially on
this weekend, not fun. Patient is a 95 S6, AC hadn't been working, so I
put a can of coolant in there. System holds pressure, and the compressor
runs, but the air from the vents is not cold. From the manual I have,
the system is supposed to hold 20 something ounces of refrigerant, so I
hope one more can will help. (yeah right) I'll check the at rest
pressure to see how full the system is before filling again. And read
codes from the HVAC unit.
 
The footwell vents seem to allways be letting out hot air. From the dash
and windshield I can get outside temp air, which is still pretty bad. I
couldn't find any write ups on Jammed flaps. Is it something that can be
cleaned or un-stuck, or are new part$ needed?
 
Any advice? Thanks, it's going to be hot for a while here in Michigan!
 
Mike