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NOTES:
n n These diagrams are not intended to show a complete circuit; they represent the position of switches during "DOOR OPEN" or
These diagrams are not intended to show a complete circuit; they represent the position of switches during "DOOR OPEN" or
"DOOR CLOSED" (continuity checks only).
"DOOR CLOSED" (continuity checks only).
Door Closed
L
(NO)
(NC)
(NO)
Monitor
Primary
Interlock
Interlock
Switch
Switch
(NC)
(NO)
P 2-2
Door
Interlock
Switch
Not Heating Troubleshooting Instruction
IMPORTANT: High-voltage is present at the magnetron and high-
voltage capacitor terminals. Avoid direct contact when power
is connected to these components to avoid serious injury or
possible death. Always be sure that the high-voltage capacitor is
discharged before accessing any of these components.
For a no-heat condition, refer to the following step-by-step
instructions:
1. Unplug microwave oven or disconnect power.
2. Discharge the high-voltage capacitor.
3. Disconnect the high-voltage transformer primary windings.
4. Attach the voltmeter leads to the high-voltage transformer
primary input wires.
5. Plug in microwave oven or reconnect power.
6. Close door and program the microwave oven to operate for
30 seconds.
7. Press START.
8. Check the input voltage at the high-voltage transformer
primary input wires. If the voltage is not close to the rating
voltage 120 ± 15 VAC, unplug microwave oven or disconnect
power. Check the circuitry as follows:
n Measure resistance of the fuse, microswitches, and
thermostats. Replace any failed components (refer to
the wiring diagram).
ACU PCBA Pin Voltage Matrix
Check for proper voltage by completing the following steps:
1. Unplug microwave oven or disconnect power.
2. Connect voltage measurement equipment to the terminals
listed below. (P1-3 and P2-3 are neutral.)
NOTE: For 50 V and over, the tolerance is ± 15 V. For 0 V, the tolerance is ± 3 V.
Abbreviations
HL - Hood Light, N - Neutral, FC - Forced Convection, HF - Hood Fan, L - Line Voltage, TT - Turntable Motor, NFS - Neutral for Switch
NOTE: When checking voltage readings on ACU PCBA, connect the grounding test lead of voltmeter to ACU PCBA neutral wire. Use the
positive test lead to probe connectors designated below.
For Service Technician Use Only
N
(NC)
(NC)
(NO)
P 2-3
Secondary
Interlock
Switch
CL - Cavity Light
Door Open
L
(NC)
(NO)
P 2-1
Primary
Interlock
Switch
(NC)
Door
Interlock
Switch
n Check for loose terminals (refer to the wiring diagram).
Check all of the terminals on the main route from the
power supply to the high-voltage transformer.
n Check for loose or failed connectors on the ACU PCBA
(P1, P2, P4). If these check out OK, plug in microwave
oven or reconnect power.
n Check for ACU PCBA failure. Refer to "ACU PCBA Pin
Voltage Matrix."
9. If the input voltage at the high-voltage transformer primary
input wires is close to the rating voltage 120 ± 15 VAC,
unplug microwave oven or disconnect power.
10. Check the power supply components. Refer to the
"Component Tests" section.
n High-voltage transformer
n High-voltage capacitor
n High-voltage diode
11. If the power supply components check out OK, check the
connection between the magnetron and the high-voltage
transformer.
12. If all of the components check out OK, replace the
magnetron.
13. Reconnect the high-voltage transformer primary windings.
3. Plug in microwave oven or reconnect power, and confirm
voltage reading.
4. Unplug microwave oven or disconnect power.
DIAGNOSTICS (Cont.)
N
(NO)
(NC)
(NC)
P 2-3
Monitor
Secondary
Interlock
Interlock
Switch
(NO)
P 2-2
Microwave Hood Combination
(NO)
P 2-1
Switch
n
2-7
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