Testing Control Board; Testing The Capacitor; Testing Fan Motor - Viking VDSC548T Series Service Manual

Service Diagnostics and Procedures
This unit utilizes capacitors for the different speeds. They should be discharged before handling to avoid
electric shock.
Control Board Diagnosis
Convection Fan (continued)
The photo below shows the K6 (direction) and
K7 (speed) relays energized. This will cause the
motor to rotate in a REV (counterclockwise)
direction and at a higher speed.
Counterclockwise (REV)–High Speed
K5
To check the individual direction and speeds,
perform the following checks:

Testing Control Board

Using either the CNV FAN LF or HF test with the
Molex connector attached to P4 board connection.
Use a volt meter to measure voltage between the
blue/black wire in the Molex plug while the
convection fan is turning in the forward direction
(clockwise) and the red wire (L2) at the line break
relay. The voltage should be 240 VAC. This will
indicate the K5 and K6 of the EOC are functioning
properly.
When switched to the CNV FAN HR or LR direction,
voltage can be measured between the orange/black
wire in the Molex plug when the convection fan is
turning in the reverse direction (counterclockwise)
and the red wire (L2) at the line break relay. The
voltage should be 240 VAC. This will indicate the K5
and K6 of the EOC are functioning properly.
© 2011 Viking Preferred Service
K6 K7
WARNING
When K7 is at rest, testing between LO and L2
should show a voltage reading of 240 VAC. The
red LED in front of the relay will NOT be lit.
When K7 is energized (CNV FAN HF or CNV HR)
testing between HI and L2 should show a voltage
reading of 240 VAC and the red LED in front of the
relay will be illuminated.
If voltage is not present, this indicates a bad relay
and the EOC will need to be replaced. Also check
wiring to the main power supply and repair/replace
as needed.
Testing The Capacitors
The range uses two 2uf capacitors. Using either
an analog or digital meter, use your highest Ohms
setting and check between each terminal of the
capacitor. Make sure one of the leads to the
capacitor is temporally removed. On an Analog
meter, the pointer will increase until it reaches its
capacitance (nearly infinity), then return to zero .
Reversing the leads will repeat the process. On a
Digital multimeter, the pointer is replaced by the
value displayed by a numerical number in the
display. It too will return to zero
good capacitor.
If the capacitor(s) is open, then it will never charge.
If it is shorted, the resistance will be infinite
immediately and won't change. If either is true,
replace the capacitor(s).

Testing Fan Motor

If all the voltage tests on the EOC are correct, the
capacitors and the convection motor need to be
checked.
With the Molex connector removed from the P4
board connection and capacitor leads removed, use
an Ohmmeter to measure resistance between blue/
black wire (forward direction) in the Molex plug and
the red wire at the line break relay.
indicating a
80