GM9S96 Service Manual
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.
burner - replace.
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
WARNING
-
The ground wire must run from the furnace all the way back
by disconnecting the electrical power and measuring resis-
tance between the neutral (white) connection and the burner
2 ohms.
The ignition control is a combination electronic and electro-
must be replaced.
WARNING
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
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-
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
-
not present the control will de-energize the gas valve and
“retry” for ignition or lockout.
WARNING
-
-
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.