MODEL NN4A, NN4C, NN4D, NN5 AND NN5A
PREVENTIVE MAINTENANCE
Follow the daily schedule; there are no adjustments. The only user-replacement items are the light bulbs located
under the top cover. If these fail, do the following:
1. Unplug the unit.
2. Remove the bulb(s) by carefully unscrewing them from their sockets.
3. Replace the bulb(s) with a manufacturer's approved replacement part. (See parts list pages 4 & 5.)
4. Check air flow through unit by feeling for air draw at slots on each side of temperature controller.
TROUBLE SHOOTING CHART
Identify problem in the left column and look for probable cause and solution in right hand column. Probable
causes listed in the order they are most likely to happen. This sequence should be used to isolate the problem.
Problem
Probable Cause
Solution
1.
No Light/No Heat
Unplugged Circuit breaker is
tripped
Plug in Reset breaker - call
electrician if tripped twice Call
Marshall Customer Service
2.
No Light/With Heat
Light bulbs burned out Light switch
defective
Unplug unit and replace bulbs Call
Marshall Customer Service
3.
Temperature Controller Flashing
999
*Defective temperature controller or
sensor
Call Marshall Customer Service
4.
Temperature Controller Displays
Less Than 400°F (204°C)
*Loose sensor or defective heating unit
assembly
Call Marshall Customer Service
5.
Low Product Temperature
Set point too low Excessive air draft
Reset to 450°F(232°C) Move unit or
shield draft
* NOTE: When replacing sensor, a special heat sink sealant will be present when removing failed sensor.
Applying new sealant is not required; however, be sure to utilize existing sealant when mounting new
sensor.
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