ST9141A Electronic Fan Timer

Article ID: 101

Last updated: 28 Dec, 2016

Honeywell ST9141A Electronic Fan Timer

The ST9141A1002 Electronic Fan Timer integrates control of all combustion blower and circulating fan operations in a gas warm air appliance. This control is the central wiring point for most of the electrical components in the furnace. The basic purposes of the ST9141A1002 are to monitor the thermostat for heat, cool, and fan demands and run the induced draft blower motor and up to a two-speed circulating fan as required. The ST9141A1002 monitors a spdt pressure switch, burner limit and primary limit.

Replacement Part: Honeywell ST9120U

LIGHT-EMITTING DIODE (LED) INDICATIONS:

LED flashing dim-bright indicates normal operation.
LED off when control is powered indicates defective control.
LED on continuously when control is powered indicates defective control.
LED flashing in a cycle with LED on followed by one or more off pulses indicates the following system errors.

# of Flashes	Description
1	BURNER limit circuit is open.
2	PRIMARY limit circuit is open.
3	Pressure switch circuit is improperly closed.
4	Control is in lockout due to air not circulating (overheating).

Setting the Heat Fan Off Delay

DIP Switches Set the heat fan off delay DIP switches to 60, 100, 140 or 180 seconds as shown below. The off delay is factory-set at 140 seconds. This delay time starts when the main gas valve is de-energized at the end of a thermostat call for heat.