GM9S96 Service Manual
SERVICING
41
High Stage 9.7 to 10.3" w.c. 10.0" w.c.
Low Stage 5.7 to 6.3" w.c. 6.0" w.c.
Single stage furnaces use a 115 volt silicon carbide igniter
(p/n 0130F00008) with 17-second warm up time.
WARNING
1. Remove burner compartment door to gain access to
the ignitor.
2. Ignitor cool - approximately 70 - 77°F.
3. Disconnect the ignitor from the Ignition Control.
4. Using an ohmmeter measure the resistance of the ig-
nitor: at room temperature a normal reading will be
37 - 68 ohms.
5. Reconnect ignitor.
WARNING
6. Place unit in heating cycle, measure current draw of
ignitor during preheat cycle.
Flashback will also cause burning in the burner venturi, but
is caused by the burning speed being greater than the gas-
Flashback may occur at the moment of ignition, after a burn-
as extinction pop.
-
tempt should be made to determine which has occurred.
1. Improper gas pressure - adjust to proper pressure
(See CHECKING GAS PRESSURE).
2. Check burner for proper alignment and/or replace
burner.
3.
The pressure control is a safety device to prevent the com-
bustion cycle from occurring with inadequate venting caused
by a restricted or blocked vent pipe.
WARNING
-
-
1. Remove burner compartment door to gain access to
pressure switch(es).
2. Remove wires from the pressure switch(es) electrical
terminals.
3. Remove the pressure control hose from the control
and interconnect with a manometer as shown in the
followi
With a call for heat and the inducer running, check across
the pressure switch contacts with an ohm meter. If the con-
tacts are not closed, compare the negative reading on the
manometer with the rating on the pressure switch to deter-
mine whether the switch is defective or if the negative pres-
sure is inadequate to close the switch.
-.
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
A high altitude kit is required for installations above 7,000 ft.
Refer to the accessory matrix in this manual to determine
the proper natural gas and LP gas high altitude kit for your
furnace.
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).