Lincoln Dual Technology Finisher 1921 Service Manual page 8

No Infrared Heating
Oven heats with switch off
Intermittent heating
Conveyor will not run
8
Main fan motor
Air pressure switch
Switch, Infrared heater
Infrared heater relay
Infrared Heating element(s)
Main heater relay or
Infrared heater relay
Thermal/overload of motor
NOTE: Display will indicate
"Belt Jam"
Power supply
Fuse, 10 Amp
Fuse holder
Hi-limit thermostat, oven cavity Terminals are normally closed. If open, reset
a digital multimeter.
The element resistance should be as follows:
208V – 43 ohms approx.
240V – 57 ohms approx.
Replace heating elements as needed.
Check for main fan operation. If it is not operating, refer
to "Oven fan will not run".
Check for 208/240VAC to the air pressure switch. If no
voltage is present, trace wiring back to main power
switch. This normally open switch should close when
the main fan is activated. Refer to the "Removal and
installation" section for proper adjustment. Replace as
needed.
Check for 208/240VAC to the Infrared heater switch. If
no voltage is present, trace wiring back to the air
pressure switch. WITH POWER OFF: Check continuity
between switch terminals. Replace switch as needed.
Check for supply voltage to the relay coil. If no voltage
is present, trace wiring back to Infrared heater switch. If
voltage is present and the relay will not activate,
replace the Infrared heater relay. Also check each relay
contact for high voltage input and output.
Check the Amp draw on each power leg for proper
load. Check the specification plate for rating
information. If the amp draw is high or low, check the
individual elements for opens, shorts and proper
resistance.
WITH POWER OFF: To check resistance of the
elements, remove all leads from the elements and use
a digital multimeter.
The element resistance should be as follows:
208V – 45 ohms approx.
240V – 58 ohms approx.
Replace heating elements as needed.
The Main heater relay or Infrared heater relay has
probably failed in the closed position. If there is no
voltage to the operating coil, but there is high voltage at
the relay output, replace the heater relay.
The main fan motor is equipped with internal thermal
protection and will cease to operate if overheating
occurs. As the motor overheats and then cools, this will
cause the oven to cycle on and off intermittently.
Improper ventilation or lack of preventive maintenance
may cause this. Also, most of the problems listed under
"Oven will not heat" can cause intermittent failure.
Check circuit breakers, reset if required. Check power
plug to be sure it is firmly in receptacle. Measure
incoming power, call power co. if needed.
Check, replace if necessary.
Check, replace if necessary.
thermostat and retest. If thermostat will not hold for
maximum oven temperature, and oven is not exceeding
temperature setting, check for proper location of
capillary bulb in its spring holder. If the capillary checks
okay, replace the hi-limit thermostat.
DTF – 1920 Series Service Manual