GC9C96 Service Manual
SERVICING
31
and the ohm meter should show a complete circuit across
the pressure switch. If the switch is not closed, compare
the negative pressure to the closing point specied for
the particular switch. Either the switch is defective or the
inducer / venting system is inadequate.
-.
OPEN TO
ATMOSPHERE
HOSE TO INDUCED
DRAFT BLOWER TAP
1/4" TEE
INDUCED DRAFT BLOWER
PRESSURE SWITCH
PRESSURE SWITCH
HOSE
INDUCED
DRAFT
BLOWER
*
*
*
* *
*
*
M
1
2
3P
C
ON
O
F
F
COIL COVER
PRESSURE SWITCH
The furnace as shipped requires no change to run between
0 - 7500 feet. Do not attempt to increase the ring rate
by changing orices or increasing the manifold pressure
below 7500 feet. feet. This can causepoor combustion and
equipment failure. High altitude installations above 7500
feet. feet may require both a pressure switch and an orice
change. These changes are necessary to compensate for
the natural reduction in the density of both the gasfuel and
the combustion air at higher altitude.
For installations above 7500 feet. feet, please refer to your
distributor for required kit(s). Contact the distributor for a
tabular listing of appropriate manufacturer’s kits for propane
gas and/or high altitude installations. The indicated kits must
be used to insure safe and proper furnace operation. All
conversions must be performed by a qualied installer, or
service agency.
In some areas the gas supplier may articially derate the
gas in an eort to compensate for the eects of altitude. If
the gas is articially derated the appropriate orce size must
be determined based on the BTU/ft
3
content of the derated
gas and the altitude. Refer to the National Fuel Gas Code,
NFPA 54/ANSI Z223.1, and information provided by the gas
supplier to determine the proper orice size.
Delayed ignition is a delay in lighting a combustible mixture
of gas and air which has accumulated in the combustion
chamber.
Furnace design makes this extremely unlikely unless safety
controls have been by-passed or tampered with. Never by-
pass or alter furnace controls.
If delayed ignition should occur, the following should be
checked:
1. Improper gas pressure - adjust to proper pressure (See
CHECKING GAS PRESSURE).
2. Improper burner positioning - burners should be in locating
slots, level front to rear and left to right.
3. Carry over (lighter tube or cross lighter) obstructed - clean.
4. Main burner orice(s) deformed, or out of alignment to
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
control to lockout due to failure to sense ame.
T T RK TR K RG T T T
T B RR R GR
T R
BR RRG R T B
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 2 ohms.
The ignition control is a combination electronic and
electromechanical device and is not eld repairable.
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.
®
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. After the ignitor warmup time, begin checking for 24 volts
to the gas valve. Voltage will be present for four seconds
during trial for ignition.
4. If proof of ame was established voltage will be provided
to the air circulation blower following the heat on delay
period.