Whirlpool KM-24 User manual

MICROHOOD
COMBINATION
JOB AID
Part No. 4322462
KM-24

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WHIRLPOOL CORPORATION assumes no responsibility for any repair
made on our products by anyone other than Authorized Factory Ser-
vice Technicians.
Copyright 1998 Whirlpool Corporation
FORWARD
This Job Aid will introduce the technician to the Whirlpool MicroHood Combina-
tion (MHC) Oven. This Job Aid is a reference guide for he experienced tech
nician. It is not designed as a replacement to basic training. This Job Aid does
not replace the Service Manual or the Use and Care Guide. It is de signed to be
used in conjunction with these manuals.
OBJECTIVE
The objective of this Job Aid is to have the experienced appliance techni cian
become familiar with the operation and service of the Whirlpool MCH Oven. It
is designed as reference material and is not a replacement for basic training.

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TABLE OF CONTENTS
Important Safety Instructions .......................................................................................... Page iv
MicroHood Model Features .............................................................................................. Page 1
The Mounting Bracket ...................................................................................................... Page 2
The Rear Mounting Bracket Latch ................................................................................... Page 3
Blower Venting Positions ................................................................................................. Page 4
The Oven Component Locations ..................................................................................... Page 5
The Humidity Sensor........................................................................................................ Page 6
The High Limit Thermostat ............................................................................................... Page 7
The Hood Fan Motor ........................................................................................................ Page 8
The Magnetron Cooling Fan Motor .................................................................................. Page 9
The Hood Fan Thermostat & Blower Motor Capacitor ................................................... Page 10
Touch Keypad & Microcomputer Board Test ................................................................. Page 11
Wiring Diagram .............................................................................................................. Page 12
Strip Circuits ................................................................................................................... Page 13
Primary, Monitor, & Secondary Switch Checkout Procedure ......................................... Page 16

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WARNING TO SERVICE TECHNICIANS
To avoid possible exposure to microwave radiation or energy, visually check the oven for damage to the
door and door seal before operating any oven. Use a microwave survey meter to check the amount of
leakage before servicing. In the event the R.F. Ieakage exceeds 4 mW/cm at 5 cm, appropriate repair must
be made before continuing to service the unit. Check interlock function by operating the door latch. The
oven cook cycle should cut off before the door can be opened.
The door and latching assembly contains the radio frequency energy within the oven. The door is protected
by three safety interlock switches. Do not attempt to defeat them.
UNDER NO CIRCUMSTANCES SHOULD YOU TRY TO OPERATE THE OVEN WITH THE DOOR
OPEN.
• Proper operation of microwave ovens requires that the magnetron be properly assembled to the
waveguide and cavity. Never operate the magnetron unless it is properly installed.
• Be sure the “RF” seal is not damaged and is assembled around the magnetron dome properly when
installing the magnetron.
• Routine service safety procedures should be exercised at all times.
• Untrained personnel should not attempt service without a thorough review of test procedures and safety
information contained in this manual.
PRECAUTIONS TO BE OBSERVED BEFORE AND
DURING SERVICING TO AVOID POSSIBLE EXPOSURE
TO EXCESSIVE MICROWAVE ENERGY
a. Do not operate or allow the oven to be operated with the door open.
b. Make the following safety checks on all ovens to be serviced before activating the magnetron or other
microwave source and make repairs as necessary.
1. Interlock Operation
2. Proper Door Closing
3. Seal and Sealing Surfaces (Arcing, Wear and Other Damage)
4. Damage to or Loosening of Hinges and Latches
5. Evidence of Dropping or Abuse
c. Before turning on the microwave power for any service test or inspection within the microwave
generating components, check the magnetron, wave guide or transmission line and cavity for proper
alignment.
d. Any defective or misadjusted components in the interlock, monitor, door seal and microwave
generation and transmission system shall be repaired or adjusted by procedures described in the
Basic Service Manuals for the specific microwave oven being serviced before the oven is released
to the owner.
e. A microwave leakage check to verify compliance with Federal Performance Standards should be
performed on each oven prior to release to the owner.
f. Do not attempt to operate the oven if the door glass is broken.
IMPORTANT SAFETY INSTRUCTIONS

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Precautions to Avoid Possible Exposure
to Excessive Microwave Energy
DO NOT attempt to operate the oven with the door open since open-door operation can result
in harmful exposure to microwave energy. It is important not to defeat or tamper with the safety
interlocks .
DO NOT place any object between the oven front face and the door or allow soil or cleaner
residue to accumulate on sealing surfaces.
DO NOT operate the oven if it is damaged. It is particularly important that the oven door close
properly and that there is no damage to the:
1. Door (bent).
2. Hinges and latches (broken or loosened).
3. Door seals and sealing surfaces.
DO NOT operate the microwave oven if the door window is broken.
The microwave oven should be checked for microwave leakage by qualified service personnel
after a repair is made.
The oven should not be adjusted or repaired by anyone except properly qualified service
personnel .
DO NOT operate the microwave oven with the outer cabinet removed.
Whirlpool microwave ovens have a monitoring system designed to assure proper operation of the
safety interlock systems.
The interlock monitor switch will immediately cause the oven fuse to blow if the door is opened and
the primary door interlock switch and/or the secondary interlock switch contacts fail in a closed
position.
CAUTION: REPLACE BLOWN FUSE WITH 15 AMPERE CLASS H FUSE ONLY
Test the upper and lower door interlock switches, cook relay and interlock monitor switch (middle
switch) for proper operation as described in the component test procedures, before replacing the
blown oven fuse.
DO NOT ATTEMPT TO REPAIR STICKING CONTACTS OF ANY INTERLOCK SWITCH,
SAFETY SWITCH OR COOK (LATCH) RELAY. REPLACE THE SWITCHES AND RELAY.
Any indication of sticking contacts during component tests requires replacement of that component
to assure reliability of the safety interlock system.
IF THE FUSE IS BLOWN, THE MONITOR, PRIMARY, AND SECONDARY INTERLOCK
SWITCHES MUST BE REPLACED. BE SURE THEY ARE PROPERLY CONNECTED.

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• High voltages are present during the cook
cycle. Extreme caution should be ob-
served at all times.
• Abrasive cleansers, steel-wool pads, gritty
wash cloths, etc. can damage the control
panel and the interior and exterior oven
surfaces. Use a sponge with mild deter-
gent or paper towels with spray glass
cleaner. Apply spray glass cleaner to
paper towel. Do not spray directly on
oven.
• Before touching any oven component or
wiring, always unplug the oven from its
power source and discharge the capaci-
tor by using a 20,000 ohm discharge
resistor or use an insulated plastic handle
screwdriver to short across the capacitor
terminals.
• Check that the unit is grounded before
trouble shooting. Be careful of the high
voltage circuits. Discharge any static
charge from your body by touching ground
before handling any part of the circuitry
on the control board. Electrostatic dis-
charge may damage the control circuit.
• Do not touch oven components or wiring
during operation. Attach meter leads with
alligator clips when making operational
tests.
• For continued protection against radia-
tion emission, replace only with these
types of switches: Primary (Interlock)
Switch: SZM-V16-FA-63 or VP-533A-OF;
Secondary (Interlock) Switch: SZM-V01-
FA-32; Interlock (Monitor) Switch: SZM-
VI6-FA-62 or VP-532A-OF; Oven Lamp
Switch: SZM-V6-FA-31 or VP-331 A-OD.
• It is neither necessary nor advisable to
attempt measurement of high voltage.
• Attaching the adaptor ground terminal to
the wall receptacle cover screw does not
ground the appliance unless the cover
screw is metal and not insulated and the
wall receptacle is grounded through the
house wiring.
• Disconnect the oven from electrical sup-
ply before servicing. Failure to do so
could result in electrical shock or death.
• Improper use of the grounding plug can
result in a risk of electrical shock. Do not,
under any circumstance, cut or remove
the third ground prong from the power
cord plug.
Fire, Electrical Shock, Excessive
Exposure to Microwave Energy,
Personal Injury & Product
Damage Hazard
• Do not block the rear air intake openings
or exhaust vents. Allow a few inches of
space at the back of the oven where
intake openings and exhaust vents are
located. Blocking the air intake openings
and exhaust vents can cause damage to
the oven and poor cooking results. Make
sure the microwave oven legs are in
place to ensure proper airflow.
• Do not install the oven next to or over a
heat source (a cooktop or range).
• Do not install oven in any area where
excessive heat and steam are gener-
ated. This could cause fire, electrical
shock, excessive exposure to microwave
energy, other personal injury or damage
to the outside of the cabinet.
CAUTION
WARNING

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MICROHOOD MODEL FEATURES
(1998 Production)
MODEL MH6140XF (VALUE MODEL)
• 1.4 Cubic Feet
• 950 Watts
• Sunken Turntable
• Electronic Controls & Clock
• Five (5) EZ-Choice™ Keypads
• Available in Black & White
MODEL MH7140XF (TRADE-UP MODEL)
• 1000 Watts
• Sunken Turntable
• Bi-Level Cooking Rack With 4-Plate Reheat
• Quiet Partner™ Hood & Microwave Oven
• EZ-VUE™ System
• Available in Black, White, & Almond
MODEL GH7145XF (GOLD SENSOR MODEL)
• Sensor One-Touch™ Cooking
• SimmerCook™ Function
• Four (4) Hood Fan Speeds
• Available in Black & White

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MOUNTING BRACKET
• A 1-1/2 ” lag bolt in a wall stud using one of the holes along the top or bottom of the bracket.
The mounting bracket for the MicroHood Oven (see the illustration at the bottom of the page)
should be installed as shown in the “Installation Instructions” that were supplied with the unit.
These instructions include installing:
• Molly bolts in each of the four corners of the bracket.
Mounting Bracket
Template

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THE REAR MOUNTING BRACKET LATCH
The Rear Mounting Bracket Latch is engaged
when the microwave oven in mounted to the
rear mounting bracket. The bracket clip is in–
serted into the rear oven panel, and is held by
the latch mechanism (see Figures A & B). To
release the clip from the latch, pull forward on
the latch arm (see illustration C and the inset).
To access the latch arm:
1. Remove the two vent cover screws.
2. Tilt the top of the vent cover forward and
remove it. The latch arm is now access-
able from the front of the unit.
Latch
Mechanism
Clip
Figure A
Figure B
Figure C
Inset
Latch
Arm Pull Arm
Forward To
Unlock Rear
Bracket
Latch Locked
Latch Unlocked

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BLOWER VENTING POSITIONS
Recirculating Air
Rear Venting
Top Venting
Blower
Air Inlet
Toward Front Of Unit
Toward Rear Of Unit
Blower
Air Inlet
Toward Top Of Unit
Blower
Air Inlet
NOTE: All microwave ovens are shipped with the venting toward the top of the unit.

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THE OVEN COMPONENT LOCATIONS
HIGH LIMIT
THERMOSTAT
OVEN CAVITY
LAMP
HUMIDITY
SENSOR
SECONDARY
INTERLOCK
SWITCH
TURNTABLE
MOTOR
COOKTOP
LAMPS
TOUCH KEYPAD
CONTROL BOARD
PRIARY
INTERLOCK/
MONITOR SWITCH
MAGNETRON
COOLING FAN MOTOR
HOOD FAN THERMOSTAT
LINE FUSE
HIGH VOLTAGE
TRANSFORMER
BLOWER MOTOR
CAPACITOR
MAGNETRON
THERMOSTAT
DIODE
H.V. CAPACITOR
HOOD
FAN MOTOR
STIRRER
FAN MOTOR

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THE HUMIDITY SENSOR
Humidity
Sensor
The Humidity Sensor is used during the “Sen-
sor Cook”operation of the oven. It is mounted
inside a cutout area on the left side of the top
cover (see the illustrations).
To access the humidity sensor:
1, Remove the top cover screws.
2. Lift the left side of the cover and slide the
sensor bracket out of the cover slots from
the bottom.
3. Remove the two screws from the sensor
and remove it from the bracket, then un-
plug the 3-pin connector from the elec-
tronic control board.
The sensor consists of two circuits in the
microcomputer board on the electronic control
panel. The microcomputer supplies a current
to the sensor which keeps it heated. The sen-
sor heat conductivity will vary, depending upon
the humidity of the oven. Changing humidity
conditions, due to the cooking process within
the oven cavity, causes a difference in poten-
tial between these two circuits. This difference
is monitored by the microcomputer during cook-
ing, allowing the microcomputer to determine
the proper cook time.
NOTE: Always verify that the sensor cover is
not obstructed (proper air flow is passing over
the sensor), and that the fan motor is working
properly, before replacing the sensor.
To test the humidity sensor:
1. Set the ohmmeter to the R x 1 scale.
2. Touch the ohmmeter leads to the follow-
ing pins on the sensor connector:
a) Pins 1 & 2 = 2.8 KΩ.
b) Pins 1 & 3 = 2.8 KΩ.
Slide Humidity & Cavity
Thermostat out of cover
viewed from under
top cover
Top Cover

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THE HIGH LIMIT THERMOSTAT
The High Limit Thermostat is normally-closed,
and will open at a set temperature to disable
the oven. The thermostat will reset itself when
the temperature drops below its “trip”setting.
The thermostat is mounted inside a cutout
area on the left side of the top cover (see the
illustration).
High Limit
Thermostat
To access the thermostat:
1. Remove the top cover screws.
2. Lift the left side of the cover and slide the
sensor bracket out of the cover slots from
the bottom.
3. Remove the two screws from the thermo-
stat and remove the two wires from the
terminals.
High Limit Thermostat: Opens @ 293˚F/145˚C
Resets @ 140˚F/60˚C

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THE HOOD FAN MOTOR
The hood fan motor removes smoke and odors
from the cooking area through recirculation or
outside venting. The exhaust fan motor is
located at the right side of the top cover.
To access the hood fan motor:
1. Remove the cabinet.
2. Lift the round fan blade off the top of the
motor.
3. Remove the three mounting screws and
flat washers from the motor.
4. Disconnect the three wires from the ter-
minals and the ground wire screw from
the chassis.
To test the hood fan motor:
1. Set the ohmmeter to R x 10.
2. Touch the ohmmeter leads to the follow-
ing wires:
Black to white = 30 to 60 Ω.
Black to red = 30 to 60 Ω.
Hood Fan
Motor
Fan Blade
Mounting
Screws & Flat
Washers

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THE MAGNETRON COOLING FAN MOTOR
The Magnetron Cooling Fan Motor cools the
magnetron during operation of the microwave
oven.
To access the motor:
1. Remove the cabinet.
2. Remove the right front side panel.
3. Remove the three screws from the bottom
of the blower motor housing.
4. Remove the fan blade from the motor by
pulling it off the shaft.
Blower Motor
Blower Housing
Screws
5. Disconnect the two wires from the termi-
nals.
6. Remove the two phillips screws from the
motor.
To test the fan motor:
1. Set the ohmmeter to R x 10.
2. Touch the ohmmeter leads to the motor
terminals. The meter should read between
17 Ωand 28 Ω.
Blower
Motor Screws
Fan Blade

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THE HOOD FAN THERMOSTAT
& BLOWER MOTOR CAPACITOR
The Hood Fan Thermostat turns on the motor
when the magnetron temperature reaches a
preset level. The Blower Motor Capacitor keeps
the motor running smoothly during current
fluctuations.
To access the hood fan thermostat and blower
motor capacitor:
1. Remove the cabinet.
2. Remove the right front side panel (the
components are mounted on the back).
3. To remove the blower motor capacitor,
remove the screw and disconnect the two
wires from the terminals.
4. To remove the hood fan thermostat, re-
move the two phillips screws and discon-
nect the two wires from the terminals.
To test the capacitor:
1. Set the ohmmeter to R x 1.
2. Touch the ohmmeter leads to the termi-
nals. The meter should indicate several
ohms and then slowly return to infinity.
Right Front
Side Panel
Blower Motor
Capacitor
Right
Front
Side Panel
Blower Motor
Thermostat

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TOUCH KEYPAD & MICROCOMPUTER BOARD TEST
1. Hold the CANCEL pad down while open-
ing the door.
2. Unplug the power supply cord from the
wall outlet for two seconds and plug it
back in.
3. Release the CANCEL pad then close the
door.
4. By pressing each of the pads on the con-
trol panel, the numeral 8 will appear in the
display to indicate that the circuits are
complete and all relays are working.
5. The pads that control the oven and
cooktop lights, in addition to the hood fan,
will also turn these components on and
off for a visual indication that the circuits
are operating properly.
The microhood combination (MHC) is provided with a self-diagnosis routine that can be accessed
through the touch keypad. To initiate this routine, perform the following steps:
Key Name In Circuit Relay Display Position
Popcorn - 5
Baked Potato - 4
Frozen
Vegetables -2
Fresh Vegetables - 1
Frozen Entree - 5
Beverage - 4
Dinner Plate - 2
Soup - 1
Sure Sim./Sim. C Humidity Sensor 5 s
Reheat - 4
Defrost - 2
Cook - 1
Cook Time - 5
Cook Power - 4
Warm Hold - 2
Add Minute - 1
1 4901 (Cavity Lt.) 5
2 4902 (Hood Lt.) 4
3-3
4-2
5-1
6 4606 (TT Motor) 5
7-4
8 4908 (Night Lt.) 3
9 4909 (Hood Fan) 2
0-1
Clock Buzzer 5
Timer (Set) - 3
Timer Off - 1
Start - 5
Turntable - 3
Off/Cancel - See Text
Light - 5
Fan On/Off - 4
Fan Speed Up - 2
Fan Speed Down - 1
QTY
SENSOR
ENTER
AUTO
COOK
REHEAT
TIMER
DEFROST
SIM
1
TURN TABLE OFF LBSOZ
POWER
START
2 3
8 8888
88
1 2 3 4 5
The number 8 will appear in the display posi-
tion indicated in the table.

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Magnetron
HV
Transformer
HV
Diode
HV
Capacitor
Microwave
Relay
FA
F
R
Down
MW
LFS
TTM
TTM
F/L
F/L
NFS
BL
N
P13
P11 FM
P15
(3P3)
P14
(5P3)
FT
P18
(1P3)
P16
P17 Door
1
1
1P2
BK RW
W
W
W
W
WR
BK
W
W
W
W
BK
BK
BL
BK
Y
R
BKBLBL
2
2
ResistorResistor
Resistor
Humidity Sensor
Magnetron
Thermostat
Up
R
2P1
TT
FM
HM
SM
CL
HLHL
Secondary
Interlock Switch
Capacitor
Monitor Switch
Fuse
R
Cavity
Sensor
R
W
W
W
W
W
W
W
W
WW
LIVE
P9
RP10NP12
Light
P8
Fan
On
Night
Light
Light
Electronic Control Board
LV Transformer
120 VAC, 60 HZ
L1
GND
N
1PO
1PO
5P1
4P1
Primary
Interlock Switch
WIRING DIAGRAM
NOTES:
1. Oven OFF
2. Door OPEN

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STRIP CIRCUITS
LOW VOLTAGE TO ELECTRONIC CONTROL BOARD
120-VOLTS TO OVEN COMPONENTS

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120-VOLTS TO EXHAUST FAN MOTOR (HIGH SPEED)
120-VOLTS TO EXHAUST FAN MOTOR (LOW SPEED)
120-VOLTS TO OVEN LIGHT
HOOD FAN
MOTOR
HOOD FAN
MOTOR