I have a Panasonic heat pump that's about 11 years old. The indoor unit is an inverter R410a. When it gets colder than -20 C (-4 F) it starts making a chugging noise, then the power light starts flashing, then eventually it makes a really long beep and turns itself off. I can usually turn it back on after a few hours using the remote, so long as it's warmed up outside. I'm heading into a week at least of very cold weather and I don't want to lose my heat every night. Is there a way to stop this? (I'm a tenant in my building so I don't have access to the outdoor unit)

  • @FreeMan so the automatic defrost in the outside unit is not working? But that's something a technician can fix? My landlord isn't likely to do anything unless I present him both the problem and the potential solution, so I need as much detail as I can get please.
    – Amai
    Feb 3, 2023 at 18:10
  • Yes. Though, with the cold snap that's crossing the US (making assumptions...) that should be motivation enough. Remind him that dead tenants don't pay rent. ;) On a more serious note, though, "my heat shuts off, call an HVAC guy" should be all the problem/resolution info he needs. Neither of you are HVAC experts, that's why you call one in.'
    – FreeMan
    Feb 3, 2023 at 18:12
  • If only my landlord was as reasonable as that! Thank you for your help. :)
    – Amai
    Feb 3, 2023 at 18:16
  • check the fuses and breakers, the automatic defrost might not be working and it has its own breaker/fuse
    – Traveler
    Feb 3, 2023 at 18:30
  • Post the full model information so we can help looking for the controll board schematic and how to fix the defrost
    – Traveler
    Feb 3, 2023 at 18:33

1 Answer 1


It sounds like the outside part of the unit is freezing up and the automatic defrost part isn't working properly. Once the coils have defrosted, you start getting heat again.

Call the landlord now to have him get someone out to fix it before you get cold. As a renter, that's about all you're allowed to do.

  • 1
    if it's just your unit, you can run AC for a while to defrost the outside coils. That does make it even colder inside, but also allows heat when done. Given the "mechanical advantage" of heat pumps, you can get about 4x more heat than AC on average with this method.
    – dandavis
    Feb 3, 2023 at 23:05
  • @dandavis doesn’t that “mechanical advantage” cut both ways, both when heating and cooling? Feb 4, 2023 at 4:53
  • 1
    @fyrepenguin yes, but you tend to be able to run the heat about 80% and the AC 20% as it takes longer to completely frost over than it does to thaw out.
    – dandavis
    Feb 4, 2023 at 8:19
  • You get more heat making frost (vapor to solid) than you lose melting it off (solid to liquid) too. You gain the latent heat of vaporization - you rent the latent heat of fusion and have to pay it right back. But the latent heat of vaporization is 6.78 times larger than the latent heat of fusion en.wikipedia.org/wiki/Latent_heat
    – Ecnerwal
    Feb 5, 2023 at 0:00

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