General Theory Of Operation; Power Check - KitchenAid KMTM704E Series Technical Education

TESTING
DANGER
Electrical Shock Hazard
Only authorized technicians should perform
diagnostic voltage measurements.
After performing voltage measurements,
disconnect power before servicing.
Failure to follow these instructions can result in
death or electrical shock.

General Theory of Operation

Refer to Wiring Diagram on page 6-3.
Neutral and L1 (AC voltage) enters the Control Board at P4,
pins 1 & 2 respectively. AC is converted to DC voltage at the
Low Volts Power Supply (LVPS). Supplies include 13 and 5 VDC,
and DC GND (REF). These low voltage supplies are used to
provide power to the microprocessors and board components,
control the TRIACs, power the sensors, buzzer, fan motor, and
energize the AC relays.
The 13 VDC is vital to the operation of the dishwasher.
This supply is necessary to operate all 120 VAC loads in
the dishwasher, whether they are connected to a relay or
controlled by TRIACs. 13 VDC is generated by the power
supply and flows through the door switch—when closed—to
be available to the heater relays (L1 & N), wash motor relay,
and the pilot relay. A relay coil becomes energized when
the control closes the LV drive circuit for a specific relay
completing 13V pathway, which in turn closes the relay switch
providing AC to the load. The Pilot relay provides "L1" to
the remainder of the components that are controlled by the
Neutral-sensed TRIACs.
In the microfiltration dishwasher, there is one fuse on the
Control Board: F9 Small-TRIAC Load Fuse. If the TRIAC Fuse is
open, all loads controlled by TRIACs will not operate.
NOTE: Refer to "Fuse Service and Diagnostic Checks" on page
6-4.
KitchenAid 2015 Microfiltration Dishwashers
n
6-6
For Service Technician Use Only

Power Check

This test checks for incoming and outgoing power to and from
the control board. This test assumes that proper voltages is
present at the outlet or direct connect cable.
Test Procedure
1. Unplug dishwasher or disconnect power.
2. Remove access panel.
3. Remove terminal box cover.
4. With a voltmeter set to AC, insert black probe inside white
wire screw nut (N) and insert red probe inside black wire
screw nut (L1).
5. Plug in dishwasher or reconnect power.
¾ If 120 VAC is present, unplug dishwasher or disconnect
power and proceed to step 6.
¾ If 120 VAC is not present, have customer correct power
problem at outlet or breaker.
6. Remove the toe panel to access the control board.
7. Remove cover from control board and locate connector P4.
8. With a voltmeter set to AC, connect black probe to P4, pin
1 (N) and red probe to P4, pin 2 (L1).
9. Plug in dishwasher or reconnect power.
¾ If 120 VAC is present, go to step 10.
¾ If 120 VAC is not present, check for open connection
between terminal block and control. Repair as needed.
10. Verify DC Supplies
• 5 VDC is used to power IC's and micro-processors on the
circuit board as well as provide power to the sensors.
¾ If 5 VDC were missing, the OWI (Optical Water
Indicator) would not function. To verify 5V ± 5%, with
a voltmeter set to DC, connect the black lead to P13-4
(DC GND) and the red lead to P11-2 (5V).
• 13 VDC is used to actuate the 120 VAC relays and TRIACs on
the control, and the LEDs on models with interior lighting.
¾ If 13 VDC was missing, the heater, motors, and all
other loads would not turn on as well as the LEDs on
models with interior lighting. To verify 13V ± 5%, with
a voltmeter set to DC, connect the black lead to P13-4
(DC GND) and the red lead to P9-6 (13V).
Troubleshooting Missing DC Supplies: Refer to the
wiring diagram on page 6-3 when troubleshooting the
DC supplies. If 5 VDC or 13 VDC is missing on the control,
unplug dishwasher or disconnect power, and then
disconnect all components/loads from the control relying
on the missing or loaded supply. Plug in dishwasher or
reconnect power and check if the DC supply has returned.
¾ If not, replace the control.
¾ If it has, turn off dishwasher and reconnect one
connector at a time until the component loading down
that supply has been identified.
11. Unplug dishwasher or disconnect power.
12. Reassemble all parts and panels.