Multi-Zone Systems Fail Differently
A single-zone home either cools or it does not. A Wellesley home with three zones off one air handler can lose cooling upstairs while the first floor is fine, and the homeowner reasonably assumes the AC is 'half broken.' It usually is not. Nine times out of ten a zone damper motor has failed closed, a zone board fuse has blown, or a communicating thermostat has lost its bus connection after a power blip. Those are inexpensive parts, but only if the technician actually tests the control side. We carry damper motors, zone board fuses, transformers, and common thermostat replacements on the truck, and we verify each zone individually before we leave — including the zones you did not complain about, because a marginal damper today is next week's emergency call.


