Viking VGDO271, Сервисный журнал, Страница: 15 / 52

T EST PROCEDURES
To avoid the risk of electrical shock, personal injury or death, disconnect power
before servicing, unless testing requires it.
Fan Motors
The fan motors are mounted to the control compartment back.
They cool the exterior oven cabinets, electrical components
and close the sail switch contacts during self-clean operation.
Use the following procedure to check for continuity.
1. Remove oven from cabinet. Remove cabinet top.
2. Disconnect power from oven. Remove motor wiring.
3. Set ohmmeter to low range.
4. Attach meter leads to wiring terminals. Meter should
indicate a low resistance reading of approximately 20 - 30
ohms for continuity.
5. If an open circuit is indicated, the motor coil has
failed. Replace motor.
6. Test each terminal to ground. If motor cavity is
shorted, replace motor.
Gas Valve
The bake and broil dual gas valves supply gas to the bake and
broil burners. The valves contain bimetal arms attached to
the valve seats held closed by incoming gas pressure. These
arms are wrapped with a small electric heater coil. When a
current range of approximately 3.2-3.6 amps flows through
the bake or broil circuit, the bimetal arm is heated. Heating
causes the arm to bend, allowing gas to flow and be ignited
be the burner ignitor.
The broil gas valve is located on the right side of the control
panel flueway and the bake gas valve is located on the left
side of the control panel flueway.
The bimetal arms can be checked for continuity using the
following procedure.
1. Access valves by removing control panel glass and
control panel mounting bracket.
2. Disconnect power to oven. Remove gas valve wiring.
3. Set ohmmeter to low ohms range. Attach meter leads to
the two gas valve terminals facing rear of oven.
4. Meter should indicate low ohms or continuity.
5. Repeat on two gas valve terminals facing front of
oven.
6. If meter indicates infinite ohms, an open heater coil,
the complete gas valve must be replaced.
NOTE: Do not apply 120 VAC to valve. Apply 120 VAC to
valve will render valve inoperative.
Bake and Broil Ignitors
The bake and broil ignitors are mounted to the bake and broil
burners. They ignite the gas flowing into the burner.
During bake and broil operations, current flows through the
ignitor, gas valve and thermostat at neutral. As the ignitor
heats up and starts glowing, its internal resistance decreased.
This allows more current to flow through the bake or broil
circuit.
When the circuit current reaches approximately 3.2-3.6 amps,
the bimetal arm in the gas valve flexes, opening the valve and
allows gas to flow to the burner where it is ignited by the
glowing ignitor. The ignitors glow anytime the bake or broil
burners are operating and cycles on and off with the
temperature setting.
Use the following procedure to check the ignitors for
continuity.
1. Disconnect power to oven.
2. Remove ignitor from burner.Disconnect ignitor
wiring.
3. Set ohmmeter R X 10 range. Attach one meter lead to
each ignitor lead.
4. A resistance of several hundred ohms may be indicated.
Amount of resistance may vary with each ignitor. This
test determines if ignitor is opened internally.
5. Ignitor may still have to be replaced even though
continuity is indicated and it glows when the oven is set
for a bake, broil or clean function.
Ignitor current may be measured more exactly by testing
with the oven operating. Use the following procedure to
test the ignitor current with the oven operating.
1. Insert an ammeter in series with one lead of ignitor or any
amprobe attached to the lead to check amount of current
flowing through the ignitor circuit.
2. Turn on oven and wait for ignitor to glow red. Meter
should indicate approximately 3.2-3.6 amps.
The same procedure may be use to bench test the ignitor.
Connect an AC jumper or test cord to the ignitor leads
and
follow the preceding procedure.
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