Volvo: 1985 240 DL heater issue, volvo 240 dl, heater control valve

Question
Recently the heating system in my 1985 Volvo 240 DL has gone on the fritz.  Most of the time the heater is blowing hot air into the cabin.  The fan is off and the only way to stop it is to close all the vents.  This has mixed results as the passenger floor vent cannot be closed.  On rare occasion the heater will not be on but 95% of the time it is.  I have taken it to a local volvo dealership and they couldn't do anything with it.  I have had problems with their mechanics in the past and have been able to fix problems myself they couldn't figure out.  With the heating system I am a little at a loss and am not sure where to begin. I've got the dash completely apart but don't really know what I'm looking for.  Any advice would be great.  Thanks a lot.
-Greg B

Answer
Greg,
So you are saying that the heat comes in no matter where the controls are set. That would mean the heater control valve is not shutting off so the heat continues. If the vent for the floor air will not shut off the small vacuum pod that controls the vents may not be working or no vacuum is flowing to it. See where the floor vent is find the vacuum pod and see if that is working..