Lennox · Thermostat error code
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Guide · ThermostatMost pro thermostats have a built-in installer or system test that turns each output on and off directly, bypassing schedules and set points. Honeywell's FocusPRO 6000 has numbered tests for heat, emergency heat, cool and fan; the VisionPRO 8000 has an Installer Test behind its installer password (the date code); Lennox's iComfort S30 has a tests menu in the dealer control center. Use it to split thermostat/wiring faults from equipment faults. Lennox specifically warns not to short across gas-valve or control terminals to test.
Guide · ThermostatMost thermostats hold the compressor off for a few minutes after it stops or after power returns, to prevent short cycling. That delay is normal. If the message lasts well past the delay or the system never starts, check mode, breakers, filter-related lockouts and wiring.
Guide · ThermostatThe O/B terminal drives the reversing valve. Most brands energize it in cooling (O); Rheem and Ruud typically energize it in heating (B). A wrong O/B setting reverses the modes. Check the equipment diagram, not wire color.
