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
