Repair manual
MT3855
3
HEATING SYSTEM
POSSIBLE CAUSE(S) SUGGESTED REMEDY
Symptom #1 - Burner will not fire
Oven in OFF mode.
Emergency stop switch on OFF.
Control circuit breaker tripped.
Combustion motor not running.
Main Temperature Controller not set above ambiĆ
ent temperature.
Manual gas valve closed.
Intermittent Ignition Device (IID) system locked
out.
Air pressure switch may be open.
Blower motor(s) not running.
High Limit control tripped.
Thermal switch in control compartment tripped.
Excessive intake air temperature.
If pilot fails to go out when the unit is shut down,
the solenoid valve is bad.
Turn to ON position.
Pull switch out to ON.
Reset breaker.
Check transformer for primary and secondary
voltage.
Check main control and burner valve relays to
see if closed.
Check relay in combustion burner box. If bad reĆ
place relay.
Set to desired temperature.
Open valve.
Reference Technical Appendix pages 6-1
through 6-3.
Check convection blower (or 3 convection fans)
for proper operation.
Verify voltage to motor. If voltage is present, reĆ
place the motor or start capacitor.
Verify that 625F (330C) high limit is proĆ
grammed into the controller. If so reset the high
limit. Set the computer to 500F (260C). Use a
pyrometer to verify the oven temperature. If the
oven climbs significantly above the setpoint, use
the chart on page 6-10 of the Technical AppenĆ
dix to check the probe. If the probe is alright the
computer may need replacement.
Check hood system.
Check hood system.
Replace valve.