My daughter's 1984 240 has hot air coming from the heater vent at all times. I checked the heater control valve and the cable seems to close it off properly. I measured the temperature of the input and output hoses with the engine warmed up. The input hose was about 100degrees and the output was about 80 degrees. From this I assume the valve is working.

Next, I tested the vacuum system which controls the flapper doors and it was ok as far as controlling the air re-circulation flapper and the defrost flappers.

The 700-900 FAQs list a similar problem and one cause is the door which prevents air from flowing through the heater coils not closing when the controls are set for no heat. I would guess that the 240 has a similar door but I don't know where it is or how to check it.

Can someone point me in the right direction? I pray it doesn't require digging into the heater system like when I replaced the blower motor!

I haven't posted in a long time. My adult daughter now has the 1984 240 which I bought her as a high school graduation gift many years ago. The car has way over 300,000 miles and is her daily driver to work. I retired from wrenching with a new Subaru Outback. 'Not nearly so easy to work on as the 240, but I have a warranty. ( I guess I'm getting old.)