have a weird problem that JUST started happening. When I turn the thermostat up with the fan set to "AUTO", nothing happens. The furnace does not light and the fan does not come on. This worked fine (for many years) until a few weeks ago and nothing else was changed. I changed the Thermostat, and a second unit did nothing different.
When I set the Thermostat fan to the "ON" setting, it starts blowing, and then when I turn the thermostat up the furnace immediately lights and heating commences.
The furnace is controlled by a Honeywell HZ322. Again, nothing changed.
There is a second Zone (downstairs), and it continues to work perfectly – fan and heat come on when thermostat is set to AUTO.
Any thoughts?
Best Answer
The zone board's gone bad
Since upstairs is broken, yet downstairs is fine, and it's not a thermostat issue, I'd point the finger at the zone board having something wrong with it. Just to make sure, try pulling the upstairs thermostat and jumpering R to W on its base; if the heat doesn't come on, then something's dead with the W input for that zone.