What happens when the thermostat system switch is set to OFF?

No functions occur, regardless of the fan switch position.

What does the FAN position on the system switch do?

The air conditioner fan runs at high speed continuously regardless of fan switch setting or setpoint. No other functions occur.

What is the difference between FAN AUTO and FAN ON in COOL mode?

In AUTO (HI or LO), the compressor and the selected-speed fan cycle together to satisfy the setpoint. In ON (LO or HI), the compressor cycles to satisfy the setpoint while the fan runs continuously at the selected speed.

Does the air conditioning fan run when the thermostat is in HEAT mode?

No. In HEAT, the furnace and furnace blower cycle to satisfy the setpoint; the furnace blower operates from a sequencer or time delay in the furnace, and the air conditioning fan does not run.

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Thermostat 7330335 / 7330385 Operation Chart - Switch Positions & Functions

HVAC thermostat OPERATION switch-position function chart for 7330 series thermostats with checkbox grid

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Manual page showing a thermostat switch-position operation chart mapping system/fan switch settings to AC and furnace functions.

AI caption June 2021 · Photo 809 of 1514

This is page 4 of 4 of an operation manual for a wall thermostat used with an air conditioning and furnace system. It applies to thermostat models 7330*335* and 7330*385*, with a note that heat function references should be disregarded when using the 7330*336* "Cool Only" thermostat. The page contains a switch-position chart showing what the system does for each combination of the SYSTEM selector (HEAT, COOL, OFF, FAN) and FAN selector (AUTO HI, AUTO LO, ON LO, ON HI). Key behaviors documented: OFF produces no functions; FAN runs the A/C fan at high speed continuously regardless of fan switch or setpoint; COOL with AUTO HI or AUTO LO cycles the compressor with the high- or low-speed fan; COOL with ON LO or ON HI cycles the compressor while the fan runs continuously at the selected speed; and any HEAT position causes the furnace and furnace blower to cycle to satisfy the setpoint, with the furnace blower operating from a sequencer or time delay in the furnace — the air conditioning fan does not run in heat mode. The reader learns exactly how each thermostat switch setting controls compressor, fan, and furnace operation after installation.

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Frequently asked questions

What happens when the thermostat system switch is set to OFF?: No functions occur, regardless of the fan switch position.
What does the FAN position on the system switch do?: The air conditioner fan runs at high speed continuously regardless of fan switch setting or setpoint. No other functions occur.
What is the difference between FAN AUTO and FAN ON in COOL mode?: In AUTO (HI or LO), the compressor and the selected-speed fan cycle together to satisfy the setpoint. In ON (LO or HI), the compressor cycles to satisfy the setpoint while the fan runs continuously at the selected speed.
Does the air conditioning fan run when the thermostat is in HEAT mode?: No. In HEAT, the furnace and furnace blower cycle to satisfy the setpoint; the furnace blower operates from a sequencer or time delay in the furnace, and the air conditioning fan does not run.
Which thermostat models does this operation chart cover?: The 7330*335* and 7330*385* thermostats; heat function references should be disregarded when using the 7330*336* "Cool Only" thermostat.