Help repair Panasonic fridge not cooling

[mikey5791]

Hi all forum members,

Few days ago, i might have forgotten to close my home fridge freezer door completely. The next day, the ice cubes and frozen meat almost melted halfway and the freezer doesn't feel cool. I shut it off, wipe dry and let it air dry for one whole day. The next day i switched on the fridge, the compressor run for a second and it shuts off(no vibration and no sound at all) only the internal freezer compartment fan is running but is not cooling even i switched on a full day.
After shut off, i dismantle the rear water pan holder and reached to the compressor wiring. Tested the resistance on the 3 connectors, there seems to be resistance of about 10-12 ohms between those 3 connectors.
Next i went to check components on the power board, no burn mark or anything suspicious visually. I got dc5v at check point J27, dc 12v at J37. Flipping to the rear side of board, when tested D5(mini black diode) on the bottom of relay RY2, i found the resistance reading of 171 on both side. Could this open diode be the cause of compressor not running? Fyi, D6 diode has different resistance reading after flipping my multimeter probes.

Kindly advise and suggest what are the component testing i can perform to check and bring back life to this old fridge since hiring a technician to repair is not in my budget. I would like to repair this board to good working condition with all your kind assistance and guidance. Thank you in advance.

[lotas]

Check the capacity of the starting capacitor, check whether the contacts on the compressor relay close when 12v is supplied to the relay.

[mikey5791]

The starting capacitor is 4uF 400vac, it is reading about 3.79uF from a capacitor meter.
Sorry i do not know how to check whether the contacts on the compressor relay close when 12v is supplied to the relay. Is it possible to test it using external 12vdc? Kindly guide on how to check.

[CapLeaker]

Look at the starter cap and the safety relay on the compressor first. To test the windings in the compressor, you really need a Megger, not a DMM. It also needs a resistance measurement, not on diode or continuity mode if you are already using a DMM. The winding should not be open, and should not be shorted to case gnd.

If you find a diode across a relay coil like D5 annd D6 and reads funny, well you are reading the coil, not the diode. It is actually there to protect the coil drive from EMF.
If you do find something fishy in circuit, always lift a leg or take the component out and check again.

[lotas]

Yes, you can check the relay without unsoldering it from the board. Apply a voltage of 10-12v to these terminals with a small current, OBSERVING POLARITY!, just don’t mix them up!, and use a multimeter to check the continuity of the closing contacts.

[CapLeaker]

The starting capacitor is 4uF 400vac, it is reading about 3.79uF from a capacitor meter.
Sorry i do not know how to check whether the contacts on the compressor relay close when 12v is supplied to the relay. Is it possible to test it using external 12vdc? Kindly guide on how to check.

Google “compressor start relay” and there are plenty vids to show you.

[redwire]

It might not be the control board or the compressor starter.
Happens to me- Whirlpool refrigerator freezer door not fully closed and compressor is running constantly, food inside thaws out.
I'll find the freezer evaporator covered in ice. So it takes a day to thaw out using a small fan blowing in. Lots of water mess. Cheap Whirlpool can't add an alarm beeper, AND it has 40W light bulb to add heat lol.

My point is the ice can trash the temperature sensor or its wiring. If it goes open-circuit or high resistance, the fridge can think the freezer is plenty cold and not run.
My friend, he always puts food in his fridge freezer and hits the sensor and wiring and unplugs it or it is hanging in the air.

Check the evaporator temperature sensor and it's wiring/connector. It might be located on the tubing. The defrost heater is also there.
I'm not sure where the freezer temperature sensor is, or maybe there is just the one thermistor.

[mikey5791]

Yes, you can check the relay without unsoldering it from the board. Apply a voltage of 10-12v to these terminals with a small current, OBSERVING POLARITY!, just don’t mix them up!, and use a multimeter to check the continuity of the closing contacts.

I applied dc12v(300ma),negative to terminal with diode image and positive to terminal near D5 marking. Immediately i can hear the relay one click sound.
But you mentioned about checking the continuity of the closing contacts, is it the opposite two separate terminals(near RY2 marking)? I didn't get any continuity from the two contacts as per your picture.

[lotas]

Well, if when power is supplied to the relay it operates, but its contacts do not close (the contacts are burnt), replace the relay with a new one.

To check if the compressor is working, temporarily install a jumper for testing, and when the mains power is supplied, the compressor should start immediately.

[mikey5791]

Well, if when power is supplied to the relay it operates, but its contacts do not close (the contacts are burnt), replace the relay with a new one.

To check if the compressor is working, temporarily install a jumper for testing, and when the mains power is supplied, the compressor should start immediately.

Hi lotas,
Thank you for your kind assistance and guidance. I will order the needed relay. Fyi, i did installed a jumper for testing and the compressor starts and running. Running it for an hour, the half glass water become semi solid ice. After that i shut it off.

Will update this forum soon after installing the new relay.
Once again, thank you to those forum members who had contributed with helpful comments.

[CapLeaker]

Take the relay out of circuit and test it again, just to be sure.

[mikey5791]

Hi to all forum members,

Yesterday i received the new relay from our local online store and installed on the fridge pcb at RY2.
The fridge has been working normal again since last night. The freezer compartment has ice cube solid frozen this morning and the fruit compartment is cooling too.
Hope this fridge will work for many years to come.
Cheers to everyone who had contributed their kind assistance and patience to help me revive this old fridge to working condition.