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Fig. 13—Position of gas control components during burner on cycle.
GAS
CONTROL
INLET
FIRST AUTOMATIC VALVE
NOTE: SECOND AUTOMATIC VALVE OPERATOR AND
SERVO PRESSURE REGULATOR SHOWN OUTSIDE
GAS CONTROL FOR EASE IN TRACING GAS FLOW.
!
WARNING
FIRE OR EXPLOSION HAZARD
CAN CAUSE PROPERTY DAMAGE,
SEVERE INJURY OR DEATH
Do not disassemble the gas control; it contains no
replaceable components. Attempted disassembly
or repair may damage the control.
!
CAUTION
Do not apply a jumper across (or short) the valve
coil terminals, even temporarily. Doing so may
burn out the heat anticipator in the thermostat or
damage the electronic module.
IMPORTANT: Allow 60 seconds after shutdown before
re-energizing step-opening model to ensure lightoff
at step pressure.
CONTROL
KNOB
FIRST
AUTOMATIC
VALVE
SOLENOID
SECOND AUTOMATIC
VALVE DIAPHRAGM
1
SLOW-OPENING GAS CONTROL HAS A GAS FLOW RESTRICTOR IN THIS PASSAGE.
SECOND AUTOMATIC
SECOND
VALVE OPERATOR
AUTOMATIC
OPERATOR
SOLENOID
SECOND
AUTOMATIC
OPERATOR
VALVE DISC
1
IF MAIN BURNER WILL NOT COME ON WITH
CALL FOR HEAT
1. Confirm that the gas control knob is in the ON
position.
2. Adjust thermostat several degrees above room tem-
perature.
3. Using ac voltmeter, check for voltage at gas control.
• If pilot lights, measure across MV/PV and MV.
• If pilot does not light, measure across MV/PV and
PV before safety lockout occurs.
4. If voltage is incorrect or not present, check control
circuit for proper operation.
5. If voltage is present, replace gas control.
13
VR8204; VR4204
OPERATION • SERVICE
SERVO PRESSURE
REGULATOR
PILOT
GAS
OUTLET
GAS
CONTROL
OUTLET
M9125
Service
68-0047—2
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