4
NOTE: If 120 volts AC + 10% is not read, check power
source.
Door Switch (See Figure 3)
The door switch is a safety that will shut off 120 volt power
to the furnace when the furnace door is open. It is a 2 position
switch.
1. Open furnace door.
2. Attach the voltmeter to the door switch. 120 volt + 10%
should be read.
3. Push in on the door switch the reading should go to zero
volts.
Remove Door Switch
1. Shut off power to furnace.
2. Disconnect 2 electric wires.
3. Press in at top and bottom of switch.
4. Remove door switch.
5. To reinstall, reverse steps 1 to 4 above.
Fan and Limit Switch Combination
(See Figure 4)
Testing the Limit Switch (See Figure 5)
When testing the limit switch with a voltmeter, a 120V +/-
10% reading indicates the switch is open and defective. The
limit switch should be replaced if cooled below switch
setting.
1. Turn off electrical power to the main power source.
2. Disconnect wires from limit switch located inside of
control panel. See wiring diagram, located in control
panel.
Figure 3
Figure 4
Figure 5
3. Using an ohmmeter, connect leads to limit switch
terminals.
4. If limit switch is below temperature, it will read continuity.
If there is not continuity, replace limit switch by removing
two 1/4" screws.
Removing the Limit Switch
1. Turn power off to the unit.
2. Unwire electrical supply.
3. Remove 2, 1/4" screws.
4. To replace, reverse steps 1-3.*
*Limit switch can be either manual or automatic reset.
Manual reset limit will be approved on serial date codes
of 9706 and later.
Testing the Fan Switch
The steps necessary to check the operation of the fan switch
in the air circulation circuit are:
1. Turn off power to unit.
2. Turn voltmeter on and set to scale capable of reading
120V.
3. Place leads from voltmeter on both wires of the fan
switch.
4. Turn on 120 volt power supply to furnace. Voltmeter
should read 120V ±10%.
5. With voltmeter leads still attached set room thermostat
above the room temperature until the burner comes on.
6. Watch the dial on the fan switch as the heat exchanger
heats up, the dial should start to rotate. When the fan
switch reaches the on temperature setting the blower
should come on, and 0 volts should be read indicating
a closed switch.
Removing the Fan Switch
1.
Shut off power to unit.
2.
Remove cover.
3.
Disconnect wires.
4.
Remove 3, 1/4" screws.
5.
To replace, reverse steps 1-4.
Testing Fan Blower Motor
(See Figure 6)
1. Check for 120 Volts + 10%.
2. Check amperage while unit is running.
3. Visually inspect wheel and motor mounting.
