GM9S80 Service Manual
SERVICING
38
Pressure Regulator
Adjustment
(Under Cap Screw)
Gas Valve
On/Off
Selector
Switch
INLET
OUTLET
Inlet Pressure
Tap
Outlet Pressure
Tap
Gas Rate Range Nominal
Propane Gas High Stage 9.7 to 10.3" w.c. 10.0" w.c.
Manifold Gas Pressure
Furnaces use a 120V car-
bide mini igniter for ignition (part# 20165703) or a Silicon
Nitride igniter (part# 0130F00008). The normal operating
1. Remove burner compartment door to gain access to
the ignitor.
2.
3. Disconnect the ignitor from the Ignition Control.
4. Using an ohmmeter measure the resistance of the
ignitor:
Mini Igniter: Carbide Mini Igniter should read between
30 to 300 ohms.
5. Reconnect ignitor.
- Furnaces with a 120V
silicone nitride igniter. The normal operating tempera-
-
perature the igniter ohm reading should be from 37
- 68 ohms.
6. After checking and/or replacing of hot surface ignitor,
reinstall burner compartment door and verify proper
unit operation.
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-
-
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 switch a safety device to prevent the combus-
tion cycle from occurring with inadequate venting caused by a
restricted or blocked vent pipe on the 80% and 90% furnaces.
-
-
1. Remove burner compartment door to gain access to
pressure switch(es).
2. Remove wires from the pressure switch(es) electrical
terminals.
3. Using a VOM check from common terminal to NC
(Normally Closed) - should read open.
If switch reads as above proceed to Step 4, otherwise re-
place control.
4. Remove the pressure control hose from the control
and interconnect with a manometer as shown in the