My HVAC system is 2 zones, hooked up to an old (circa 1984) Mastertrol zone controller, and Trol-A-Temp dampers.

Attached to the panel is a "system selector switch". Basically, its a knob switch with 4 positions: heat/off/fan/cool. I manually change the setting based on time of the year (if i need heating or cooling). Wires leave this box and connect to the system selector switch posts on the zone controller (MABS-V3, Mastertrol Mark V). However, this seems to prevent me from ever being able to run the fan directly from a thermostat.

Since I cant seem to find any information on the zone controller (nor who installed it originally), I was wondering if anyone knew anything about it, and if there is a way to bypass the system selector switch so I can take advantage of newer t-stats (I want to be able to run the fan all day, or at least intermittent thru the day. we're getting areas in the house with large temp differentials and i was hoping running the fan would smooth them out).

Any information would be greatly appreciated. (BTW, I talked to Honeywell, and although they said its not possible, they admitted they werent sure because the setup is so old).