Fault Diagnosis-Oven - Moffat turbofan E32SUBC Service Manual

5
Trouble-shooting
5.3 Fault Diagnosis—Oven
5.3.1 Oven does not operate / start
Controller fuse
Remove RHS panel, locate fuse carrier in LH bot-
tom corner and check fuse continuity
5.3.2 Fan doesn't operate
Microswitch out of adjustment
Open oven door and manually depress door
microswitch actuator at bottom right of oven. If
this activates the fan, then the microswitch
actuator arm inside control cavity requires
adjustment.
To adjust refer 6.4.1
Microswitch faulty
Check voltage from microswitch terminals to
neutral.
With the door closed there should be power to
the com terminal and the n.o. terminal.
With the door open there should be power to the
com terminal and the n.c. terminal.
If not, microswitch is faulty—replace.
Figure 5.3.2a
Relay faulty
The fan is controlled by relay #3
To test refer to 3.4.6
Check red flag on relay top to see if relay is ener-
gised. If no flag present check voltage (24Vdc) to
control relay coil. If voltage present replace relay.
If relay is operating check continuity through re-
lay contacts. Replace if no continuity through
contacts.
Relay #3
Figure 5.3.2b
E32SUBC OVEN and PROOFER
Revision 3
Microswitch
n.c.
n.o
.
com
Fan motor timer faulty
With oven switched on, and door closed,
ensure that the cams on the motor timer are
rotating.
If cams are rotating, then isolate the power
supply from the oven. Remove the bottom wire
from the left
Rotate the cams manually whilst testing for
continuity through the left hand switch. Check
that the continuity cycles as the cams are
rotated. Re-secure the left hand wire, and then
repeat test for right hand switch.
When operating, 50Hz models should cycle the
power for approximately 80 seconds through
each switch, with a 10 second delay between
each cycle.
On 60Hz models the power should cycle
for approximately 65 seconds through each
switch, with an 8 second delay between each
cycle.
If there is no continuity, or the continuity does
not cycle correctly then timer is faulty -
replace.
Fan motor capacitor faulty
Ensure that oven is isolated from the power
supply. Disconnect the two capacitor wires.
Briefly short across the capacitor terminals, to
ensure that it is fully discharged.
Using a multimeter, measure the resistance
across capacitor terminals.
The resistance should start low and quickly
increase to infinity within 5-10 seconds. If the
resistance does not increase at all, then the
capacitor is shorted - replace. If the capacitor is
infinite resistance straight away then it is open-
circuit - replace.
very high then the capacitor is leaky - replace.
26
Motor Cams (Rotate
one revolution every
three minutes)
Figure 5.3.2c
hand switch terminals.
If the resistance never goes
© Moffat Ltd, September 2009