O&C MANUAL #8311 • TH/III FAMILY
PG. 17
SECTION 6 SERVICE SECTION 6
4. c) Check for power at the secondary side of the
transformer. The voltage reading should be
approximately 20 VAC at points 67 and 72
indicated on Figure 3. If the correct voltage
is not present, the transformer is defective.
d) Disconnect electrical power to the unit by turn-
ing off the circuit in the main supply panel.
Check the two inline fuse assemblies. Using a
VOM meter, remove one end of the fuse assembly
and check for continuity. See Figure 3. If the fuse
shows that it is open, then replace the bad fuse
assembly. If all the above tests (1-4) check out
okay, a defective control is the probable cause.
B. Display is lit and unit calls for heat, but unit
is not heating; or Error Code E30
1. Check to verify that the high limit switch located at
the rear of the bonnet, next to the cord inlet has not
been tripped. If it has been tripped, reset by either
pressing in the red button or by flipping up the green
tab. After resetting, the cause of the high limit trip
must be corrected. If the high limit switch will not
reset, the high limit switch is defective and must be
replaced. This is a safety device and must not
be jumped out or removed from the circuit.
2. Disconnect electrical power to the unit by turning
off the circuit in the main supply panel. Locate the
cable connections in either the front left corner or the
right rear corner of the unit and test each cable to
ground, using a VOM meter. Any resistance reading
to ground will indicate a shorted or open cable to
ground and the cable will need to be replaced. If this
checks out okay, proceed to step 3.
3. Reconnect electrical power to the unit. Check the
solid state relay mounted on the metal heat sink.
With the unit circuit breaker switch on
and the
control in the off mode
, using a VOM meter set to the
AC volt scale, check across the closure terminals #1
and #2. See Figure 4. There should be line voltage
(200-240 VAC) present. With the VOM meter set on
the DC volt scale, check across the trigger terminals #3
and #4, taking care to observe polarity. There should
be less than 1 volt DC current present. If not, the
solid state relay is defective.
4. On the same solid state relay, with the unit in the
preheat mode and using a VOM meter set to the DC
volt scale, check across the trigger terminal #3 and #4,
taking care to observe polarity. See Figure 5. There
should be a reading of between 3.5 and 5 volt DC
present. With the VOM meter on the AC volt scale
and checking across the closure terminal #1 and #2,
there should be less that 1 volt AC current present.
If not, the solid state relay is defective.
TROUBLE SHOOTING INTERNAL ELECTRICAL COMPONENTS CONTINUED
Figure 3
Figure 4
Secondary
Side
Line Voltage: 200-240 VAC
Figure 5
3.5 to 5 VDC
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