29
Maintenance
PROBLEM
POSSIBLE CAUSE
SOLUTION
HAVE PILOT FLAME,
MAIN BURNER WILL
NOT TURN ON
Faulty main valve coil in the
gas valve
Set test meter to 24 volt scale.
Faulty ignitor/sensor and/or its
wiring
With pilot flame on ignitor/sensor, probe terminals
MV and MV/PV on the ignition control unit. If you
read 24 volts here, but not at the gas valve, there
is a loose wiring connection. Repair or
replace as needed.
Ground wire not attached to
machine chassis
If you do read 24 volts at MV and MV/PV and the
pilot flame is impinging on the ignitor/sensor rod,
the problems may be:
Faulty ignition control unit
a. Faulty ignitor/sensor and/or its wiring.
b. Faulty ignition control unit.
Set test meter to the ohm scale. Turn burner
switch off.
Check continuity through the green ground wire
and its connections.
Reconnect the ignitor/sensor wire and the ground
wire.
Turn burner switch on. With the pilot burning and
the flame on the ignitor/sensor rod, the main
burner should turn on. If it does not, replace the
ignition control unit.
SHORT-CYCLING
OF MAIN BURNER. MAIN
BURNER
TURNS OFF BEFORE
THE BURNER SWITCH
OR FLOW SWITCH
IS TURNED OFF
Draft condition pulls flame from
ignitor/sensor rod.
Check the thermostat by bypassing at terminals
P1 & 1.
Set thermostat high. With main burner on, observe
the pilot flame impingement on the ignitor/sensor.
Faulty thermostat or water
temperature is too high
If pilot flame is small and draft condition pulls
flame from ignitor sensor rod, the burner will turn
off and then on again. a. Adjust pilot flame higher
or clean pilot orifice. b. Bend ignitor/sensor rod
closer to pilot flame.
If flame impingement on the ignitor/sensor is
stable and the system short-cycles, check the limit
switch.
Set test meter to 110 volt scale;
a. When the system cycles off, probe
the switch terminals of the limit switch.
b. If you read 24V across the switch
terminals the limit switch is open.
Replace the limit switch.
A pilot flame set too high will also cause burner to
short cycle. Pilot flame lifts over ignitor/sensor.
MANUAL, OPERATOR, HOTSY, STAT ELEC NG-LP 9.808-037.0-A
