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Electronic Refrigeration Diagnostics

Training and Technical Support Team 07-PPT-RE-01 (Revised Jan 2009)

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Lets start with the non adaptive boards(GE models: GBSC0,GBSC3,GBRC0,)

& (Moffat models MBRC0) MANUAL 31-9179

CON1 and CON2 – Thermistor

Con3

Pin 1 Neutral

Pin 3 EMI Filter, Lights, Icemaker

Pin 4 Defrost Heater, Return Duct Heaters

Pin 5 Compressor & Fans

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Non adaptive Main control board

The main board is located in the fresh food area.

These models only have one thermistor connected to the board.

The resistance values of the thermistor has the same values as our other thermistors.

See resistance value chart on slide 17.

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Non adaptive Main control board cont.

Element connected in series with a 55f defrost thermostat.

Defrost every 18 hours.. 40 min just like a mechanical timer.

Non adaptive meaning it only monitors the compressor running time.

The damper is controlled mechanical by the consumer.

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Non adaptive Main control board cont.

Fresh Food Thermistor Model GBSC0The fresh food thermistor is located in the control housing in the fresh food compartment. It is necessary to remove the control housing to access the fresh food thermistor.

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Non adaptive Main control board cont.

The mechanical damper is located at the back of the control housing

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Non adaptive Main control board cont. How to force defrost.

UNPLUG THE REFRIGERATOR FROM MAIN POWER

USE A JUMPER AND CONNECT “J1” AND “J2”

PLUG THE REFRIGERATOR BACK (WITH JUMPER ON)

ONCE THE DEFROST IS FINISHED, JUMPER NEEDS TO BE REMOVED

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Adaptive defrost

• Testing Sensors Page 13 to 16

• Thermistor values Page 17

• Testing Fans Page 18 to 21

• Testing Dampers Page 22 to 23

• Inverter compressor Page 30 to 35

• Testing Defrost Page 36 to 37

• Diagnostic Page 38 to 40

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Adaptive Defrost with the main board located at the back if the fridge.

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GE Electronic Refrigeration Diagnostics

J1 (Sensors) Connector Page 4 to 8

J2 (Fans) Connector Page 9, to 12

J3 Connector DampersPage 13,14BPO encoder diagnostics

J4 Connector Page 15

J5 Connector Page 16,17

J7 ConnectorPage 18,19

Comp. J8 Defrost J9 Line J11

J12 ConnectionsPage 20

Defrost operation page 15 & 16Inverter compressor page 17,18,19

Training and Technical Support Team 07-PPT-RE-01 (Revised Jan 2009)

J15 Invertor Connector Page 21,22

123456789

Min. 30k ohms to active defrost

Between pin 5 & 4

The connectors are identified by numbers starting with 1 on topExcept J7 on the left that starts with 9 on top.

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Adaptive Defrost Operation

The main board looks to door opening and compressor run times to determine when a defrost can take place. This could be as often as every 8 hours, or as long as a week of operation before defrosting. The defrost cycle consists of 4 phases:

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Adaptive Defrost Operation (cont)

1. Prechill: The main board locks on the compressor for 2 hours to lower the temperature in the freezer by as much as 20 degrees F. (-20 F )

2. Defrost: element on3. 5 Minute Dwell time: The main board turns off the

defrost element but does not turn fans or compressor on. To allow moisture to drop from the evaporator .

4. Post Dwell: The main board turns back on the fans and compressor.

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J1 Connector Thermistor and Model Select Connector (Overview)

Pin 1 through 5 are the thermistor connections. Pin 5 is the common lead for the thermistors.

The refrigerator thermistors have a negative temperature coefficient. As the temperature inside the refrigerator becomes colder, the resistance values of the thermistor increases.

The encoder board or temperature setting interface sends a signal to the main board stating the temperatures the consumer has selected.The processor on the main board converts the selected temperatures to resistance values.The main board then monitors the thermistor’s resistance values. Based on these resistancevalues, the processor on the main board determines what actions it has to perform.

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Measure thermistor resistance with the wires disconnected from the board. Measure voltages with the wires connected to the board. Compare the resistance found to the temperature-resistance chart. (page 6)

If the refrigerator is not defrosting, measure the resistance of the evaporatorthermistor before defrosting the refrigerator. An evaporator thermistor thatis out of calibration can prevent the main board from turning the defrostheaters on. To initiate a defrost cycle the main control board must read atleast 30 to 40 K Ohms from the defrost thermistor located on the evaporator. Main control board will terminate the defrost cycle when thermistor read a temperature of at least 60°F or 7K Ohms.

Pin 6 thru 9 are the model select connections.

J1 Connector Thermistor and Model Select Connector (Overview) (cont.)

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Pin 2 «FF2» Thermistor. Not used on all models. Measure the thermistor resistance by reading between the wire connected to this Pin and the wireconnected tp Pin 5. Measure this thermistor voltage by reading betweenPin 2 and Pin 5 Voltage should be between 2.8 and 3.5 V DC with a good thermistor.

Pin 1 «FF1» Thermistor. Not used on all models. If used, measurethermistor resistance by reading the wire connected to this pin and the wireconnected to Pin 5. Measure this thermistor voltage by reading betweenPin 1 and Pin 5. Voltage should be between 2.8 and 3.5 V DC with a good thermistor.

J1 Connector Thermistors

Note:a. A bad thermistor will read below 1 or

above 4 VDC b. A reading above 4 VDC is normal for freezer

thermistor pin 3 to 5, if temperature in freezer is extremely cold (EX: -29°f).

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J1 Connector Thermistors (cont.)

Pin 3 «FZ» Thermistor. Based on the resistance of this thermistor, the processor on the main board determines when to turn the compressor on or off. Measure thermistor resistance by reading between the wireconnected to this pin and the wire connected to Pin 5. Measure thisthermistor voltage by reading between Pim 3 and Pin 5. Voltage shouldbe between 2.8 and 3.5 V DC with a good thermistor.

Pin 4 Evaporator Thermistor based on resistance of this thermistor, the processor on the main board determines if the heater will come on for defrost and when to terminate defrost Measure thermistor resistance by reading between the wire connected to this Pin and the wire connectedto Pin 5. Measure this thermistor voltage by reading between Pin 4 and Pin 5. Voltage should be between 2.8 and 3.5 V DC with a good thermistor.

Pin 5. Common connection for thermistors and model select. (+5 V DC) Measure supply voltage for thermistors by reading between this Pin and Pin 3 on connector J4.

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Thermistor Values

166.8 K-40

120.5 K-31

12.7 K41

16.3 K32

21 K23

27.6 K14

36.4 K5

48.4 K-4

65 K-13

88 K-22

Resistance in k ohmsTemperature in Degrees F

10 K50

7.8 K59

1.2 K140

1.5 K131

1.8 K122

2.2 K113

2.6 K104

3.2 K95

4 K88

5 K77

6.2 K68

Resistance in k ohmsTemperature in degrees F

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J2 Connector Fan Motor Connections

The J2 connector is for all of the fan motors.

Some pins might not have a wire connected to them depending upon model features.

If evaporator fan is not operating, check the resistor located by this connector. If it isburnt, replace the evaporator fan motor and the main board.

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J2 Connector Fan Motor Connections (cont.)

If you measure no voltage at this connector, disconnect wiring and recheckvoltages. If you now measure the correct voltage, check condenser fan and wiring to condenser fan for short to ground.

To physically test fan motors, you may use a 9 volt DC battery. Connect white wire to the negative terminal, jump red and yellow together and connect to postive terminal. A good motor will run slowly.

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J2 Connector Fan Motor Connections

Pin 1. Evaporator Fan Tachometer provides feed back from fan motor. This feedback tells the processor what speed the fan motoris running. Check for voltage between Pin 1 and Pin 3. The voltage should be 6.3 V DC.

Pin 2. Personality input to the board on some models with a FF fan motor.

Pin 3. Common lead to all fan motors. Pin 3 to Pin 8, 13.7 V DC.

Pin 4. Evaporator Fan. Pin 4 to Pin 3. Between 4 V DC and 12.4 V DC, +/- 10 %, depending on fan speed.

To test Evaporator fan motor look for 12 volts dc between pin 3 and pin 8 AND 4,8,or 12 volts dc between pin 3 and pin 4.

To test Condenser fan motor look for 12 volts dc between pin 3 and pin 8 and 8 or 12 volts dc between pin 3 and pin 5.

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J2 Connector Fan Motor Connections (cont.)

Pin 5. Condenser Fan.(Side by Side and top mount freezer models) Pin 5 to Pin 3. Between 4 V DC and 12.4 V DC, +/- 10 %, depending on fan speed on inverter models, 12.4V DC on non-inverter models.For Bottom Mount refrigerators. Pin 5 to Pin 3. Between 4 V DC and 12.4 V DC, +/- 10 %, depending on fan speed on inverter modelsFor single speed fan motors a reading between 7.5 V DC and 8.5 V DC is normal.

Pin 6. Fresh Food Fan (when used) Pin 6 to Pin 3. Between 4 V DC and 12.4 V DC, +/- 10 %, depending on fan speed.

Pin 7. Quick ChillMC Fan (when used). Pin 7 to Pin 3. 13.7 V DC, +/- 10%.

Pin 8. Fan power supply. +13.7 V DC. Pin 3 to Pin 8.

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J3 Connector Damper motor and Encoder Connections

Pins 1 thru 4 are the damper stepper motor connections.Pins 5 thru 10 are the Encoder board connection.

J3 Pin 1 to J4 Pin 3, 6 V DC Traveling Voltage or 2.3 V DC standing voltage.

J3 Pin 2 to J4 Pin 3, 6 V DC Traveling Voltage or 2.3 VDC standing voltage.J3 Pin 3 to J4 Pin 3, 6 V DC Traveling Voltage or 2.3 V DC standing voltage.

J3 Pin 4 to J4 Pin 3, 6 V DC Traveling voltage or 2.3 V DC standing voltage.

1

2

3

4

5

1

2

3

4

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J3 Connector Damper motor and Encoder Connections (cont.)

J3 Pin 5. Encoder Connection. Not used on all models.J3 Pin 6. Encoder Connection. Not used on all models.J3 Pin 7. Encoder Connection. Not used on all models.J3 Pin 8. Encoder Connection. Not used on all models.J3 Pin 9. Encoder Connection . Not used on all models.See Encoder table on how to diagnose the encoder.

J3 Pin 10. Double Function Pin Encoder Connection Not on all models or on inverter compressor models used to transmit speed data to compressor inverter module on some models. 1.5 to 3 V DC measured between J3 Pin 10 and J4 Pin 3.

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J4 ConnectorFF,FZ, Dispenser, and Quick ChillDrawer Serial Data Communications Connections

Pin 2 Dispenser Board, FF,FZ, And Quick Chill Drawer +13V DC Power supply.

Pin 1 Dispenser, FF, FZ, And Quick Chill Drawer Data Communications on some models.

Pin 4 Dispenser Board Input 1. (Input from the Dispenser Board on some models)

Pin 3 Board DC Common Ground.

Pin 5 Dispenser Board Input 2 (Input from the Dispenser Board on some models)

Some pins might not have a wire connected to them depending uponmodel features.

To test power supply measure voltage between pin 2 power supply and pin 3 board DC common ground should read +13VDC

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J5 Connector Quick Chill DrawerConnections – Not used on all models

Pin 1. Chiller Drawer Damper Motor Connection 13.7 V DC Pin 1to Pin 2.

Pin 2. Chiller Drawer Damper Motor Connection 13.7 V DC Pin 1 to Pin 2.

Pin 3. Chiller Drawer Damper Motor Connection 13.7 V DC Pin 3 to Pin 4 Not used on all models.

Measure thermistor resistance with the wires disconnected from the board.Measure voltages with the wires connected to the board

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J5 Connector Quick Chill Drawer Connections –Not used on all models (cont.)

Pin 4. Chiller Drawer Damper Motor Connection 13.7 V DC Pin 3 to Pin 4 Not used on all models.

Pin 5. Chiller Drawer Thermistor Connection. Measureresistance by reading between wires connected tp Pin 5 and Pin 6. Measure voltage by reading between Pin 5 and J 4 Pin 3 Voltage should be 5V DC.

Pin 6. Chiller Drawer Thermistor Connection. Measureresistance by reading between wires connected to Pin 5 and Pin 6. Measure voltage by reading between J4 Pin 3 and Pin 6. Voltage should be between 2.8 and 3.5 V DC with a good thermistor.

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J7 Connector 120 V AC Outputs and Inputs

Pin 9. Neutral Connection to Main Board.

Pin 8. Blank.

Pin 7. Input FZ Door 120V AC With door open between Pin 7 and Pin 9.

Pin 6. Input FF Door 120V CA With the door open between Pin 6 and Pin 9.

Pin 5. Output Quick Chill Heater 120V CA measured betweenPin 5 and Pin 9.

J7

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J7 Connector 120 V AC Outputs and Inputs (cont.)

Pin 4. Input for auger from FZ door interlock switch. 120V AC between Pin 4 and Pin 9 with the FZ door closed.

Pin 3. Output to dispenser water valve solenoid. 120V AC between Pin 3 and Pin 9 with the FZ Door closed and cradledepressed.

Pin 2. Output to cube solenoid with Fz Door closed, cubes selected, and cradle switch depressed, 120V AC between Pin 2 and Pin 9.

Pin 1. Output to auger motor. 120V AC between Pin 1 and Pin 9. FZ Door closed, cubes or crushed selected, and switchdepressed.

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J8, J9, J11 and J12 Connections120 VAC input and output connections

J8 Output to compressor 120 VAC measured between J8 and J7, Pin 9. J8J9 Output to Defrost Circuit 120 VAC mesured between J9 and J7, Pin 9. J9J11 Line in to Board. 120 VAC measured between J11 and J7, Pin 9.

J11

J12 Output to Monogram drain pan heater 120 VAC measured between J12 et J7 Pin 9. The pan heater is on only during defrost.

J12J8

J9J11

J12

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J15 Connector Inverter compressor

The main control board will send a PWM run signal from the J15 connector of between 4-6 VDC effective voltage to the inverter (all wires must be connected). The inverter will select compressor speed (voltage output) based on this signal.The main control board will only send a run signal to the inverter when the compressor should be on.

If the J15 wiring is disconnected, the board output will measure between 10-12 VDC

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J15 Connector (cont.)

Low speed (1710 rpm) - 57 HzMedium speed (2100 rpm) - 70 HzHigh speed (3120 rpm) - 104 Hz

The inverter controls compressor speed by frequency variation and by Pulse Width Modulation (PWM). Changing frequency and PWM will causean effective voltage between 80 and 230 VAC to be received at the compressor.

Frequency can be measured at the J15 connector with a proper Digital multimeters. (available from mabe, part # AM220)

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Inverter compressor diagnosisWARNING: When the refrigerator is plugged in, 120 VAC is always present at the inverter.

The compressor leads must be connected to measure voltage output. If the compressor wires are not connected, or if an openoccurs in one of the 3 lead wires or in the compressor, the inverter will stop voltage output.

When checking inverter voltage output, connect the test-meter leads to any 2 of the 3 compressor lead wires at the inverter plug (plug should be connected). The same reading should be measured between any 2 of the 3 wires.

J15 connector

4-6 vdc output to inverter (dictate compressor running speed)

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Inverter compressor diagnosis (cont.)

When measuring signal voltage (from the main control board J15) at the inverter, a reading of 4-6 VDC will be measured with all wires connected. If the inverter wiring is disconnected, the board output will measure between 10-12 VDC.To test, measure 120 VAC into inverter and 4-6 VDC at J15

J15 connector

4-6 vdc output to inverter (dictate compressor running speed)

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Inverter Troubleshooting Sequence

1. Check for 120 volts at the inverter power connector

2. Check for 4-6 VDC at J15 on the control board when the compressor should be running.

• Harness disconnected should have 10 to 12vdc. No voltage, replace the main control board

3. Check for compressor vibration to see if the compressor is running. (Disconnect power from unit and place a hand on the compressor and reconnect power and feel for vibration).

DO NOT ATTEMPT TO DIRECT-START THE COMPRESSOR. THE COMPRESSOR OPERATES ON A 3-PHASE POWER SUPPLY. APPLYING 120 VAC TO COMPRESSOR WILL PERMANENTLY DAMAGE THE UNIT. IT IS NOT POSSIBLE TO START THE COMPRESSOR WITHOUT AN INVERTER.

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Inverter Troubleshooting Sequence (cont.)

4. check for a resistance of 9 to 11 ohms between any 2 of the 3 pins on the compressor.

• If any 2 are open or shorted, replace compressor• When ordering a replacement compressor order both

the compressor and inverter. Replace the compressor first. If it fails to start, replace the inverter.

5. If all checks pass, replace inverter

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Diagnosing Defrost Operation

1. Verify that you have a full frost pattern and a No Defrost condition2. Remove main board cover from rear of unit3. With unit unplugged, use an ohmmeter to check resistance between

Defrost pin on J9 and neutral pin on J7 connector. A good circuit should read aprox 27 ohms. (Alternately, with the unit plugged in you may use a flat blade screw driver to short between defrost pin J9 and the line pin J11.

4. With an amp probe on the defrost wire going to J9 you should read an amperage reading of abut 4 amps if the defrost circuit is good.

DefrostLine

Neutral

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Diagnosing Defrost Operation (cont.)

4. If resistance is good or heater draws amperage, check the evaporator thermistor ( this is the device that terminates defrost) on the J1 connector between pin 4 and pin 5. ( do this test with the connector removed from the board, measuring at the connector) Compare resistance found to the resistance/temperature chart on page 6. Resistance should be greater than 36,000 ohms.

5. If good, change the main board.

J1

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Some models with a filter reset pad can be entered into diagnostic mode to test different components. Examples. Defrost, Damper, Change from F/C.

Enter the diagnostic mode by pressing both the freezer temperature (colder and warmer) pads and the refrigerator temperature (colder and warmer) pads simultaneously.

All four pads must be held for approximately 3 seconds. Blinking "0's" in both displays indicate the refrigerator has entered the test mode.

Filter reset pad

39See notes on the next page for test marked with an X

Note: # 1 for sensors & Note # 2 for testing defrost.

X

X

X

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Note 1. Display order is #1) Fresh Food 1 #2) Fresh Food 2 #3) Custom Cool #4) Evaporator #5) Freezer Thermistor test results are: P = Pass 0 = Fail S = Short to 5 VDC B = Bad amplifier (replace control)

Note 2. You must enter the defrost test again to toggle the defrost heater off at the end of the test.

Refer to Service Guide 31-9072 for additional information

The heater will not come on if the evaporator thermistor is warm.

Sensor testing and forced defrost.Note: To check the sensor resistance go to the back of the fridge at the main board at the J1 plug.