Mercury Contactor
Heater Elements
Oven heats with switch off | Mercury Contactor |
Intermittent Heating | Thermal/Overload |
| of motor |
Conveyor will not run
S/N 2011383 and above
Conveyor speed varying or intermittent
S/N 2011383 and above
Time/Temp. Display inoperative
Impinger II - 1100 Series Service Manual - International
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 check good, then the problem is usually with the temperature control board.
Check for 120 VAC to the contactor coil. If voltage is present and contactor will not activate, replace the contactor.
Also, check each contactor for proper high voltage input and output.
Check the Amp. draw on each hot leg for proper load.
Check the specifications 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: To check resistance of the elements, remove all leads from the elements and use an accurate digital VOM. The element resistance should be as follows:
200V - 24.5 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. If the motor overheats and then cools, this will cause the oven 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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