10.If the blower motor runs with the fan switch in the “ON” position but does not run shortly after the fur- nace has ignited when the fan switch is in the “AUTO” position, check the room thermostat for contact between R and G during “W1” calls.
On calls for heating, the supply air blower operates but the draft motor does not (the room thermostat fan switch is in the “AUTO” position).
1.The draft motor has inherent protection. If the motor shell is hot to the touch, wait for the internal overload to reset.
2.If the motor shell is cold with the room thermostat calling for heat, check for line voltage at the motor's
3.If line voltage is not present, check for line voltage at the heat relay (RW1) contacts in the main con- trol box and check to see if the (RW1) is pulled in.
4.If the (RW1) relay is pulled in, check for a loose line voltage connection.
5.If the (RW1) relay is not pulled in, check for 24 volts at the (RW1) coil. If 24 volts is present, replace the (RW1) relay. If 24 volts is not present, check for a loose 24 volt connection back to the relay board and check the connections from the room thermo- stat to the relay board. If all connections are cor- rect, replace the relay board.
The draft motor runs but the furnace does not light and the sparker does not spark.
1.The ignition control (IC1, IC2) may be locked out due to either a flame roll out or 100% shut off. These safety features are described above. If lock- out has occurred, 24V must be removed from the ignition controls. This is done at the unit or by resetting the room thermostat. After resetting 24V, check for proper furnace operation. If
2.Check all 24 volt connections from the relay board to and in the gas heat section. Check low voltage connections to the (ETD) located in the control box.
3.If the furnace is hot, it may be out on an
4.If the furnace is cold, check for 24 volts at wire 241 attached to the electrical time delay (ETD) located in the main control box. If 24 volts is not found, replace the ETD.
5.24 volts is found at wire 241, remove the wires attached to the (TDR) and with a VOM, check for continuity across contacts 1 and 2. If none is found, the (TDR) is open and must be replaced. If there is continuity,
6.Check for 24V at terminal 2 of
7.If 24 volts is present at the ignitor controls, check all control wiring at the ignitor controls and the high tension wire to the ignitors. Check that the ground wires from the ignitor controls, the gas valves and pilot burners are all intact and making good electri- cal connection. Check to make sure that the ceramic insulator on the pilot ignitors or sensors is not broken or cracked, if all are intact, replace the ignition control IC1 or IC2.
The draft motor runs and the ignitor sparks at the pilot burner but the pilot does not ignite and a gas odor is not detected at the draft motor outlet.
1.Check to make sure gas is being supplied to the unit. Make sure that the gas pressure to the unit is within the proper limits as described in the “POST START CHECK LIST” page 43 and that the pilot adjust screw is allowing some flow of gas as described in “PILOT CHECKOUT” page 44.
2.Check all wiring between the ignitor control and the gas valve. Check to make sure the ground connec- tions are intact.
3.If the wiring is intact, check for 24 volts across ter- minals “PV” and “COMMON” on the ignitor control. If 24 volts is not present, replace the ignitor control.
Johnson Controls Unitary Products | 51 |
