SERVICING
42
2. Improper burner positioning - burners should be in lo-
cating slots, level front to rear and left to right.
3. Carry over (lighter tube or cross lighter) obstructed -
clean.
4.
Main burner orifice(s) deformed, or out of alignment to
burner - replace.
CHECKING INTEGRATED IGNITION CONTROL
BOARDS
NOTE:
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 flame.
WARNING
To avoid the risk of electrical shock, wiring to the unit must
be properly polarized and grounded. Disconnect power be
-
fore performing service listed below.
The ground wire must run from the furnace all the way back
to the electrical panel. Proper grounding can be confirmed
by disconnecting the electrical power and measuring resis-
tance between the neutral (white) connection and the burner
closest to the flame sensor. Resistance should be less than
2 ohms.
The ignition control is a combination electronic and electro-
mechanical device and is not field repairable. Complete unit
must be replaced.
WARNING
Line Voltage now present.
These tests must be completed within a given time frame
due to the operation of the ignition control.
The ignition control is capable of diagnosing many furnace
failures to help in troubleshooting. The trial for ignition period
is 4 seconds.
The indicator light/display may be viewed by looking through
the sight glass in the blower compartment door. If the blow-
er compartment door is removed, failure to hold the door
switch closed while removing the blower compartment door
will result in the loss of the stored failure code. In most cas-
es recycling the ignition control will result in the same failure
code originally displayed.
WARNING
Line Voltage now present.
These tests must be completed within a given time frame
due to the operation of the ignition control.
1. Check for 120 volts from Line 1 (Hot) to Line 2 (Neu-
tral) 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 thermo-
stat, and wiring. If you have 24 volts coming off 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 con-
nector) and Line (Neutral) on the control board. No
voltage, replace ignition control.
4. If voltage is present in Steps 1 through 3 and the in-
duced 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 (Neu-
tral) on the control board. No voltage, check pressure
switch.
5. After the ignitor warm-up time, begin checking for 24
volts to the gas valve. Voltage will be present for seven
seconds only if proof of flame has been established.
CHECKING FLAME SENSOR
A flame sensing device is used in conjunction with the igni
-
tion control module to prove combustion. If proof of flame is
not present the control will de-energize the gas valve and
“retry” for ignition or lockout.
WARNING
HIGH VOLTAGE
Disconnect ALL power before servicing or in
-
stalling this unit. Multiple power sources may
be present. Failure to do so may cause proper
-
ty damage, personal injury or death.
1. Connect a micro-amp meter in series with this wire
and the sensor terminal.
2. Be sure the positive side of the meter is to the sensor
(depending on the model) and the negative side of the
meter is to sensor terminal.
