Lincoln 1100 Series Service Manual page 23

Temperature Control
Potentiometer
Mercury Contactor
Heater Elements
Oven heats with switch Mercury Contactor
off
Intermittent Heating Thermal/Overload of motor
Conveyor will not run / REFER TO PAGE 26
Conveyor speed varying / REFER TO PAGE 26
or intermittent
Time/Temp Display / REFER TO PAGE 27
inoperative
Temp Display out or / REFER TO PAGE 27
inaccurate
Impinger II –1100 Series Service Manual - Domestic
WITH POWER OFF: remove the potentiometer leads
from the temperature control board and measure ohms
from black to white leads. The reading should be from
approximately 0 to 2.5k ohms as the dial of the
potentiometer is turned throughout its full rotation. From
black to red leads, the reading should be approximately
2.5k ohms (constant) throughout the full rotation of the
dial. If these readings are not achieved, replace
potentiometer. If the thermocouple probe and the control
potentiometer checks good, then the problem is usually
with the temperature control board.
Check for 120 VAC to the contactor coil. If voltage is
present and contact will not activate, replace the
contactor. Also, check each contactor for proper high
voltage input and output
Check the Amp. draw on each leg for proper load.
Check the specification plate for rating information. If
the Amp. draw is low or high, check the individual
elements for opens, shorts, and proper resistance.
WITH POWER OFF: check resistance of the elements,
remove all leads from the elements and use an
accurate digital VOM. The element resistance should
be as follows: 208V - 27 ohms approximately, 240V -
36 ohms approximately.
The mercury contactor has probably malfunctioned in
the closed position. If there is no voltage to the
operating coil, but there is high voltage at the contactor
output, replace the mercury contactor.
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 ovens to cycle on and off intermittently. This
may be caused by improper ventilation or preventative
maintenance. Also, most of the problems listed under
"Oven will not heat" can cause intermittent failure.
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