Electric Oven Service Manual

22 OVEN SYSTEMS
b) If terminal resistance is incorrect,
replace the power supply.
3. If correct voltage is present, disconnect the
output wires and check output (-OUT &
+OUT) for 24 VDC.
4. If voltage is present with output wires
disconnected and not present when the
wires are connected, inspect the wire
harness for damage or shorts.
5. If the wire harness is intact and undamaged,
the power supply is damaged or defective
and must be replaced (page A-8).
Power Supply - 24VDC (International)
The power supply - 24VDC (international)
converts line voltage to 24 VDC. Line voltage is
connected to terminals L & N. The output (24
VDC) is on terminals “-V” and “+V”.
Testing Procedure
1. Check for line voltage (208-240 VAC) at
terminals L & N.
2. If correct voltage is present, check output
(-V & +V) for 24 VDC (with output wires
disconnected).
3. If voltage is present with output wires
disconnected and not present when the
wires are connected, inspect the wire
harness for damage or shorts (page 45).
4. If wire harness is intact and undamaged,
the power supply - 24VDC (international)
is damaged or defective and must be
replaced (page A-8).
K3 Relay - Gas
The K3 relay is a single pole, double throw
relay with a 24 VDC coil. The coil resistance is
577
W and the contact rating is 20A at 240
VAC. When 24 VDC is applied to the coil, the
normally open contacts (7 & 4 or C & NO)
close applying line voltage to the burner trans-
former and the combustion blower.
Testing Procedure
1. Disconnect line voltage to the unit.
2. Take a resistance reading of the coil.
3. If coil resistance is correct (577
W):
a) Apply line voltage to the unit.
b) Check for 24 VDC at the coil of the
relay when the unit is calling for heat.
c) Check the state of the contacts.
-If the normally open contacts (7 & 4
-or C & NO) are closed when coil
-voltage is applied, the K3 relay is
-functioning normally.
-If the normally open contacts (7 & 4
-or C & NO are not closed when coil
-voltage is applied, the K3 relay is
-malfunctioning and must be replaced
-(page A-8).
4. If the coil resistance is incorrect, replace the
K3 relay.
K4 Relay - Ignition
The K4 relay is a single pole, double throw
relay with a 24 VAC coil. The coil resistance is
585 k
W and the contact rating is 20 A at 240
VAC. When 24 VAC is applied to the coil, the
normally open contacts (7 & 4 or C & NO)
close and the normally closed contacts (7 & 1
or C & NC) open.
The K4 relay uses the normally closed contacts.
If 24 VAC is applied to the ignition module
and 1.5 uA minimum is not maintained, the
ignition module applies 24 VAC to the relay
and the contacts open. When the contacts open
the I/O control board shows an “F3 No Flame”
fault.
Testing Procedure
1. Disconnect line voltage to the unit.
2. Take a resistance reading of the K4 coil.