Service Guide
SERVICING
40
Failure to earth ground the furnace, reversing the
neutral and hot wire connection to the line (polarity), or a
high resistance connection in the neutral line may cause the
control to lockout due to failure to sense ame.
R
SK R SK R
S RR R R
S R
R RR SR S
The ground wire must run from the furnace all the way back
to the electrical panel. Proper grounding can be conrmed by
disconnecting the electrical power and measuring resistance
between the neutral (white) connection and the burner closest
to the ame sensor. Resistance should be less than 10 ohms.
The ignition control is a combination electronic and
electromechanical device and is not eld repairable. Complete
unit must be replaced.
RS
These tests must be completed within a given time frame due
to the operation of the ignition control.
The models use
1. Check for 120 volts from Line 1 (Hot) to Line 2 (Neutral)
at the ignition control. No voltage, check the door switch
connections and wire harness for continuity.
2. Check for 24 volts from W to C terminal on the ignition
control. No voltage. Check transformer, room thermostat,
and wiring.
If you have 24 volts coming o the transformer but receive
approximately 13 volts on the terminal board between (C)
and (R), check for blown fuse.
3. Check for 120 volts to the induced draft blower by
measuring voltage between Pin 1 (on the 2-pin connector)
and Line (Neutral) on the control board. No voltage,
replace ignition control.
4. If voltage is present in Steps 1 through 3 and the induced
draft blower is operating, check for 120 volts to the ignitor
during the preheat cycle. Measure voltage between Pin 2
(on the 2-pin connector) and Line (Neutral) on the control
board. No voltage, check pressure switch.
5. After the ignitor warmup time, begin checking for 24 volts
to the gas valve. Voltage will be present for seven seconds
only if proof of ame has been established.