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When Heating, TACO HAFC Showing both Heat & Cool Fans On

My hot air has been feeling rather cool lately in my condo, so upon poking around my unit, it looks as though the Taco HAFC control may be to blame, as it's lights for Heat Call, Fan - Cool, and Fan - Heat are all on at the same time when thermostat has kicked on for heating. I tested AC, and it correctly only shows Fan-Cool light on. In reading up on this Taco unit, it said it controls/adjusts when incoming water is overly hot - and I recently turn my water boiler all the way up past 140 degrees. Could this be the culprit? I just turned down water boiler, and am waiting for it to all run through system, but thought there may be thoughts here online.


  • walt9064
    walt9064 Member Posts: 3
    I have the very same problem! Have you found any answers? I’ll likely call Taco tech support
    HVACNUT Member Posts: 5,870
    Is the condenser running during a heat call?
    Disconnect Y from the thermostat side of the Taco relay. If the A/C stops, then there's a short in the wiring to the thermostat, or a faulty thermostat. 
    If the A/C stays on, then disconnect Y from the air handler side of the Taco relay. If the A/C shuts off, it's the relay.