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Panasonic Water Heater Repair

By on January 3, 2017












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:




  1. tyrone

    January 3, 2017 at 9:11 pm

    if the bulb is dim or not glowing(in the bulb test method) does it indicate that there is a problem in the circuit?

    • Bulent NUR

      January 4, 2017 at 1:10 am

      Yes its a problem indicate, no glow show is faulty component, dim bulb is show loosen connection or corroded wire.

  2. Albert van Bemmelen

    January 3, 2017 at 11:42 pm

    You accomplished a very tedious job by removing the pile of tar Mr.SK Wong! Not something that one should expect. I wonder though if you also had tried to remove the tar with Acetone? Terpentine and in particular Alcohol I found to be useless in similar cases. Like when we for instance want to remove old cooling paste on CPUs or GPUs before adding any new Paste.

    • skwong

      January 7, 2017 at 4:59 pm

      I agree with you, alcohol is useless in this case. I think turpentine can dissolve the tar but it is oil based which I do not like to use. Finally, I used thinner since I have it in stock, although it does not react or dissolve well with the tar.

  3. Parasuraman S

    January 3, 2017 at 11:57 pm

    Good work! You require a lot of patience to handle such jobs!

  4. Bulent NUR

    January 4, 2017 at 1:05 am

    Very good job thanks for sharing.

  5. Anthony

    January 4, 2017 at 2:45 am

    Wow, what a mess ! Great repair work Mr S K Wong as it was in such a bad state. Thanks for sharing.

  6. mahmoud_tajpour

    January 4, 2017 at 3:25 am

    Hello dear Wong I must say you are also brave to open this device for repair because it is so hard therefore well done.

  7. Robert Calk

    January 4, 2017 at 12:16 pm

    Nice work, Mr. Wong. Thanks for sharing the repair with us.

  8. Yogesh Panchal

    January 4, 2017 at 3:27 pm

    Thanks for sharing your experience.

  9. Humberto

    January 14, 2017 at 12:05 am

    Good repair and thanks for sharing it with us.

  10. Chris

    January 22, 2017 at 11:19 pm

    Hi Mr. Wong, well done job but I have one question to you.
    I never saw tar in any electronic device for electronic
    component covering stuff.

    From where was that tar coming from and what would be the purpose?

    From my experience tar will dissolve pig fat.
    Simply put pig fat on tar and wait and you will see the tar will be dissolved.

  11. senthil

    May 30, 2017 at 7:31 pm

    LED No power on the heater and water is not heat up. what is the first testing on the water heater need to do? I am using tecno 8308.

  12. Jason

    July 6, 2017 at 9:32 am


    1. I am wondering if lets say I do not know the condition of the water heater that I am going to use (hotel/rental room), what are your safest ways to prevent electrocution if the water heater is faulty?

    Are these ways good to prevent electrocution if the water heater is faulty:
    2. Would putting the shower head on the wall shower head holder without my hand holding it, and water spraying on my body, prevent electrocution?
    3. Would putting the shower head on the wall shower head holder without my hand holding it, and after water spraying into a pail, then I use the water from the pail by scooping up using a mug and pouring on my body prevent electrocution?
    4. Would using a plastic shower head and holding the plastic shower head handle in my hand and spraying water on my body prevent electrocution?
    5. Would using a fully plastic hose instead of a plastic hose that has shiny metal outer layer casing helps to prevent electrocution?
    6. Would wearing a plastic or rubbery slippers during bathing and prevent electrocution if electric leakage comes from the shower head handle I am holding?
    7. Would a plastic shower head handle be better than a chrome/chrome plated shower head handle to prevent electrocution?

    Thanks a lot.

  13. Ivan Lim

    August 14, 2017 at 12:58 pm

    hi Mr Wong,

    My Panasonic water heater (DH-3DL2S) temperature is not working. The water coming out is always too hot no matter how I adjust the temp knob. How do I repair it? Tks

  14. teo

    August 16, 2017 at 8:26 am

    Mr Wong, good article. nice reading. thanks

  15. m s m laffir

    September 26, 2018 at 11:49 pm


  16. Juan

    July 29, 2019 at 7:04 pm

    Hello, Mr Wong! Thank you for this article. It seems to me like I have a problem with my heating element. With your formula, I should be reading a resistance of 15 ohms, but I get zero as I'm on a 4,500 watt version. Is it safe to assume then that the heating element is bad?

  17. Jon Taneo

    February 20, 2020 at 11:00 pm

    Hello mr wong, I am mr taneo of the philippines,
    my panasonic tankless water heater cannot be adjusted to low heat.
    It is just like fixed to full high.
    What do you think is the usual cause for this.problem?
    Thank youand more power!!

  18. Athan

    July 23, 2020 at 1:43 pm

    Where do we get parts for these panasonic heater

  19. Sivabalan Vadiveloo

    December 1, 2020 at 5:37 pm

    Hi Mr Wong, My Panasonic Jet Pump Home Shower making noise.
    Dh-jp2m. Can I disable the pump bcos my water pressure is ok. Tqvm Sir.

  20. Ng

    March 25, 2021 at 7:43 pm

    Hi mr wong my Panasonic water heater keeps triping what happened? Please helps


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