Digital thermostat mounted on a concrete wall

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Using the thermostat's installer test to run heat, cool and fan (instead of jumping wires at the board)

Most 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.

Single source ~20 min easyBrands: Honeywell Home / Resideo, Lennox, All

Before you start

Do not jumper terminals at the gas valve or the furnace control to 'test'; use the thermostat's test or the equipment's own test mode.
Some installer tests bypass the compressor's minimum off time (Honeywell warns about this on the FocusPRO 6000): do not cycle the compressor on and off quickly; wait about 5 minutes between compressor starts.
Gas-side faults found during the test (no ignition, rollout, flame problems) go to a licensed gas technician; refrigerant faults go to an EPA 608 certified technician.

Diagnostic steps

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