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Panasonic Water Heater Repair
I have come across a number of Panasonic water heaters Model: DH-360M with fault that the power LED lighted up but the heater won’t work or turn on.
The symptom will be the water temperature may be intermittent warm or totally not heating at all. The first impression will be the heater was faulty.
The heater resistance measured was 17.12 ohm (photo 1) which was normal with reference to the specification of the heater (photo2). By calculation the power is (V*V)/R=240*240/17.12=3.36KW.
The triac which act like a switch to switch on the heater was measured and found to be not faulty. Since the triac is not short or open circuit, the fault must be in the main board. Next, I check the flow switch function. The heater cannot turn on if the flow switch was faulty. The fault of the flow switch can be easily confirm by shorting the flow switch wires temporary. In this case, it did not turn on the heater even though the flow was closed i.e shorted together.
The final step will be to check on the main board. On removing the main board I feel nauseating to see some areas of the pcb component side and copper side are covered with black sticky paste which smell like tar. (Photo 3 & 4)
Removing the tar was very messy and tedious but If you do not remove it you will not be able to trouble-shoot. The tar has to be carefully remove as not to accidentally throw away some of the damaged resistors due to corrosion. I think the tar has turned corrosive after a period of time . Due to the corrosion, a number of the resistors with leads were either broken or missing (Photo 5)
Photo 5- Resistor leads damaged due to corrosion
After replacing all damaged resistors, the water heater still not functioning as normal . The corrosion due to the tar was much more serious problems than expected. The voltages measured on the board were weird and abnormal. The tar being sticky was quite messy to remove and clean completely even with thinner or industrial alcohol. After thorough cleaning of the copper side of the pcb, the problem can be seen. There were corrosion on all the terminal leads which resulted in dry joint (see photo 6).
After all the connectors were re-soldered, the water heater was functioning back to normal. I did elaborate on the method of testing the water heater as I have highlighted it in one of my earlier article. Anybody wanted to know more about water heater testing , please refer to my previous article below:
This article was prepared for you by SK Wong from Malaysia and he graduated from London with a degree in Electronics and Electrical Engineering. He has more than 40 years of experience in the consumer product manufacturing. With the passion to repair electronic products from young , he has been doing it part time until now.
Currently, he can provide turnkey solutions for consumer products including services from idea or concept to design , prototyping , finished products (including electronic,mechanical and plastic parts) and manufacturing.
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Note: You can check his previous repair articles below: