Page 88 Part # MCOSM06 Rev 1 (11/03/08)
Trouble Shooting Guide
PROBLEM POSSIBLE CAUSE CORRECTIVE ACTION
Fan will not run A. No power to unit
B. No power to motor from
relay board
C. Micro switch no closing
A. Turn power on
B. Check for voltage from relay board
to motor
C. Check micro switches
Button on key pad
not responding A. Loose ribbon
connection between key
pad and smart board
B. Faulty key pad
A. Check that ribbon connection from
key pad is attached to smart board
B. Refer to key pad testing procedure
on bulletin # B-107-2001
‘Prob’ in display A. Probe disconnected
B. Probe has failed A. Re attach probe
B. Confirm ohm resistance of probe.
Refer to cavity probe chart for
readings
C. Check for continuity between probe
connection at relay board, probe
harness & probe
Unit will not shut off A. Cavity temperature
above 150°FA. Normal operation. Unit will not go
to OFF until cavity temperature is
below 150°F
No HIGH speed
BUT HIGH speed
LED is illuminated
on key pad
A. Bad relay board
B. Bad smart board
A. CR3 on relay board should be on, if
not check for 24VDC +/- 10% at
pins 5 & 7 at relay board. If voltage
present replace relay board
B. Check for 24VDC +/- 10%between
pins 5 & 7 at relay board. If voltage
is not present replace smart board
No LOW speed BUT
LOW speed LED is
illuminated on key
pad
A. Bad relay board
B. Bad smart board
A. CR4 on relay board should be on, if
not check for 24VDC +/- 10% at
pins 5 & 8 at relay board. If voltage
is present replace relay board
B. Check for 24VDC +/- 10% at pins 5
& 8 at relay board. If voltage is not
present replace smart board.
Unit will not heat.
DOOR shown in
display
A. Open circuit on upper
door switch A. Unplug unit from supply. With door
closed between NO and COM
switch should be open.
B. With door open to 30° angle switch
should be closed
C. Withdoor open all the way switch
should be closed
Unit will not turn ON
when button pushed,
display reads OFF
A. Loose ribbon
connection between key
pad and smart board
B. Faulty key pad
A. Check connection
B. Refer to key pad testing procedure
on bulletin # B-107-2001