York Gas Furnace: YM9M

Re: Test Mode

During normal operation, the furnace input rate can vary between 35% and 100% of full nameplate input, making it difficult to check for proper operation. To help with the furnace startup and testing process, the control has a TEST MODE available that allows the furnace input rate to stay at a constant input rate.

To access this TEST MODE perform the following sequence:

• With power to the board on and with no thermostat calls (no call for heating, cooling or continuous fan), push and hold the TEST button on the board for one second. The LED on the board will glow RED.

• Release the TEST button. The LED on the board will flash a RAPID GREEN signal, indicating that TEST MODE is activated.

• Turn the thermostat to call for heat (or place a jumper across R & W at the furnace control board).

• The furnace will light and operate at high (100%) firing rate. The furnace manifold gas pressure should be checked at this level to confirm that the furnace is not overfired or underfired.

• To run the furnace at minimum rate (35%), press the ERROR button once. The LED will flash ONE GREEN flash to confirm.

• To run the furnace at a middle rate (70%), press the ERROR button twice within a five-second period. The LED will flash TWO GREEN to confirm.

• To again operate the furnace at maximum (100%) rate, press the ERROR button three times within a five-second period. The LED will flash THREE GREEN to confirm.

• If the thermostat call for heat is removed, the LED will flash a RAPID GREEN signal, indicating that the furnace is still in TEST MODE.

• When tests are completed, turning off power to the board will take the furnace out of TEST MODE and will restore normal operation. The furnace will automatically return to normal operation after 150 minutes if power is not cycled.