Whirlpool MH7140XF Microwave Oven
Contents
1. 5 Sensor 6 The High Limit Thermostat sae eect RUM de M 7 Th Hood Fan oon coton zu ates on ve tO US rete ees Page 8 The Magnetron Cooling Fan Page 9 The Hood Fan Thermostat Blower Motor Capacitor Page 10 Touch Keypad amp Microcomputer Board Page 11 Wining Diagram ce ee ace aie DOS Page 12 SMP e 13 Primary Monitor Secondary Switch Checkout Procedure Page 16 IMPORTANT SAFETY INSTRUCTIONS 4 CAUTION 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 leakage exceeds 4 mW cm 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 Th2. 24 MICROHOOD COMBINATION SS ER EE 00 00 JOB AID Part No 4322462 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 Oven It is designed as reference material and is not a replacement for basic training 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 TABLE OF CONTENTS Important Safety InstrucHolis Page iv MicroHood Model hata inca voten dba pL Ote ubi one dde Page 1 The Mounting Bracket tea hin es ces a Page 2 The Rear Mounting Bracket Page 3 Blower Venting Positions er a pr udi ea weedy 4 The Oven Component
3. CANCEL pad then close the Fresh Vegetables door Frozen Entree 4 pressing each of the pads on the con trol panel the numeral 8 will appear in the display to indicate that the circuits are Dinner Plate will also turn these components on and Defrost off for a visual indication that the circuits are operating properly 12345 Add Minute 1 4901 Cavity Lt complete and all relays are working 5 4 2 1 5 4 2 1 5 The pads control the oven and Pt eet 5A cooktop lights in addition to the hood fan Reheat 4 2 1 5 4 2 1 1 5 4 3 0 LiL Li oo LI LIS Z QTY TURN TABLE OFF 18502 START 4902 Hood Lt The number 8 will appear in the display posi 2 3 4 tion indicated in the table 7 Clock Turntable Off Cancel Fan Speed Up Fan Speed Down 11 Buzzer 4908 Night Lt 4909 Hood Fan 2 1 5 3 2 1 3 3 1 5 3 2 1 WIRING DIAGRAM 1 Oven OFF 2 Door OPEN NOTES 5 AH JeuuojsueJ AH 8 Josuas aJ NY YOUMS ACW M Eld Tord Zdl SAN 5 2 Goa E OR SAT WLL 20
4. LOW VOLTAGE THERMOSTAT 1 TRANSFORMER W OVEN LIGHT 1 1 1 DOOR 1 i RELAY BK W 1 6 PO OP 120 VOLTS TO EXHAUST FAN THERMOSTAT amp FAN MOTOR L1 HI LIMIT THERMOSTAT LOW VOLTAGE MOTOR THERMOSTAT TRANSFORMER HI LIMIT LOW VOLTAGE THERMOSTAT TRANSFORMER 15 PRIMARY MONITOR 8 SECONDARY SWITCH CHECKOUT PROCEDURE Door Switch Test Procedure Door Open Disconnect wires from the primary interlock switch No Measure from COM terminal white continuity wires to terminal blue wires Disconnect wires from the secondary interlock switch Measure from COM terminal white No Continuity amp black wires to N O terminal continuity white wires Measure from COM terminal white Continuity No amp black wires to N C terminal continuity yellow wires Secondary Interlock Disconnect wires from the monitor switch Measure from COM terminal blue No Continuity wires to N O terminal continuity blue wires Measure from COM terminal blue Continuity No wires to N C terminal red amp white continuity wires Monitor 16
5. 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 E FN x A 1 1 2 lag bolt in a wall stud using one of the holes along the top or bottom of the bracket Mounting Bracket ooo Oo OC OOO oOo 00 0 0 0 000 0 0 ogo oct 0 oso THE REAR MOUNTING BRACKET LATCH The Rear Mounting Bracket Latch is engaged To access the latch arm when the microwave oven in mounted to the 1 rear mounting bracket The bracket clip is serted into rear oven panel and is Ore Vent s and the latch mechanism see Figures 8 remove it The latch arm is now access release the clip from the latch pull forward on able from the front of the unit the latch arm see illustration C and the inset Remove the two vent cover screws Figure B Latch Mechanism Latch Unlocked Pull Arm Forward To Unlock Rear Bracket BLOWER VENTING POSITIONS Recirculating Air Toward Front Of Unit Rear Venting Blower Air Inlet Toward Rear Of Unit Top Venting Toward Top Of Unit Blower Air Inlet NOT
6. of the oven Changing humidity Humidity Sensor 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 8 2 2 8 b Pins 1 8 3 2 8 Top Cover viewed from under Slide Humidity amp Cavity top cover Thermostat out of cover 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 15 2 Remove the cover screws Lift the left side of the cover and slide the sensor bracket out of the cover slots from the bottom Remove the two screws from the thermo stat and remove the two wires from the terminals High Limit Thermostat Opens
7. 04 ee Q ldz 9 me H M 8 0 A1 0J1u02 ur VA UO 1467 ued 1uDIN 4 JA17 ee ee lt lt lt lt lt lt lt lt 14 Josues 0 65 A esnj YOO J9 U KjepuooaS 120 60 2 12 STRIP CIRCUITS LOW VOLTAGE TO ELECTRONIC CONTROL BOARD MICROCOMPUTER HI LIMIT LOWVOLTAGE THERMOSTAT TRANSFORMER 120 VOLTS TO OVEN COMPONENTS 11 MICROCOMPUTER Decree HI LIMIT FUSE LOWVOLTAGE THERMOSTAT TRANSFORMER Q SECONDARY INTERLOCK FAICH MONITOR SWITCH BL MICROWAVE MAG THERM gL Q O O HUS RE PRIMARY INTERLOCK SWITCH HIGH HIS VOLTAGE SYSTEM 120 VOLTS EXHAUST MOTOR HIGH SPEED MICROCOMPUTER HI LIMIT LOW VOLTAGE THERMOSTAT TRANSFORMER 11 HI LIMIT LOWVOLTAGE THERMOSTAT TRANSFORMER HOOD FAN MOTOR 120 VOLTS TO OVEN LIGHT HI LIMIT LOW VOLTAGE THERMOSTAT TRANSFORMER LIGHT ON 1 RELAY 14 120 VOLTS OVEN LIGHT ACTIVATES WHEN DOOR OPENS 11 MICROCOMPUTER BOARD We ges ap 1 HI LIMIT FUSE i
8. 293 F 145 C Resets 140 F 60 C 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 Mounting Screws amp Flat Washers 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 Q Black to red 30 to 60 0 Fan Blade Hood Fan Motor THE MAGNETRON COOLING FAN MOTOR The Magnetron Cooling Fan Motor cools the 5 Disconnect the two wires from the termi magnetron during operation of the microwave nals Ovan 6 Remove the two phillips screws from the To access the motor motor 1 Remove the cabinet 2 Remove the right front side panel 3 Remove three screws from the bottom of the blower motor housing To test the fan motor Set the ohmmeter to R x 10 2 Touch the ohmmeter leads to the motor terminals The meter should read between 4 Remove the fan blade from the motor by 17 and 28 Q pulling it off the shaft lt lt Fan Blade eX Blower Motor Screws Blow
9. E microwave ovens shipped with the venting toward the top of the unit 4 THE OVEN COMPONENT LOCATIONS HUMIDITY _ STIRRER HIGH LIMIT FAN MOTOR HOOD SENSOR FAN MOTOR THERMOSTAT gt H V CAPACITOR OVEN CAVITY 2 LA DIODE SECONDARY 45 24 INTERLOCK SWITCH ores felt d 2 29 MAGNETRON TURNTABLE THERMOSTAT MOTOR T MOTOR CAPACITOR LAMPS 2 D a VOLTAGE IS TRANSFORMER LINE FUSE HOOD FAN THERMOSTAT MAGNETRON COOLING FAN MOTOR INTERLOCK N MONITOR SWITCH CONTROL BOARD T PETIT JU 7 UIT TOUCH KEYPAD THE 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
10. ROPERLY CONNECTED 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 CAUTION 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 wi
11. e 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 Do not operate or allow the oven to be operated with the door open Make the following safety checks on all ovens to be serviced before activating the magnetron or other microwave source and make repairs as necessary Interlock Operation Proper Door Closing Seal and Sealing Surfaces Arcing Wear and Other Damage Damage to or Loosening of Hinges and Latches Evidence of Dropping or Abuse Before turning 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 Any defective or misadjusted components in the interlock moni
12. er Motor Blower Housing Screws 8 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 Blower Motor gt Capacitor Blower Motor Thermostat 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 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 Right Front Side Panel 10 TOUCH KEYPAD 8 MICROCOMPUTER BOARD TEST 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 1 Hold the CANCEL pad down while open In Circuit Relay Display Position ing the door 2 Unplug the power supply cord from the mem wall outlet for two seconds and plug it pene 3 Release the
13. mstance cut or remove the third ground prong from the power cord plug Fire Electrical Shock Excessive Exposure to Microwave Energy Personal Injury amp 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 MICROHOOD MODEL FEATURES 1998 Production MODEL MH6140XF VALUE MODEL 1 4 Cubic Feet 950 Watts Sunken Turntable Electronic Controls amp 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 amp Almond MODEL GH7145XF GOLD SENSOR MODEL Sensor One Touch Cooking SimmerCook Function Four 4 Hood Fan Speeds Available in Black amp White MOUNTING BRACKET
14. ring 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 A WARNING 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 circu
15. tor 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 A microwave leakage check to verify compliance with Federal Performance Standards should be performed on each oven prior to release to the owner Do not attempt to operate the oven if the door glass is broken 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 P
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