Troubleshooting Your Portable Air Conditioner: Moisture Control and Heating

Portable air conditioning is a great solution to combat the summer heat, but as with any appliance, you might run into some issues that require a little help to alleviate. Last week, we reviewed answers to installation and cooling questions. Today, we’ll review how to handle heating and mildew concerns to make sure your PAC is running at peak performance.


Why isn’t the heater switching on?

  • The heating function might not be activated in the ambient temperature is too high. Heating is activated below 44-81°F, so make sure the ambient temperature in the room is below this threshold to allow the heating function to turn on.

Why does the unit keep switching off in heating mode?

  • The room is likely too humid, meaning the water tank needs to be emptied.
    • In heating mode, the heat pump condenses moisture from the air into the internal water tanks. In a more humid room, the tank fills faster and needs to be emptied more frequently.
    • It’s recommended to use the heating mode in 50% humidity or less. You should also switch off any appliances like humidifiers or kettles that could be emitting extra moisture into the room.


Why is there a musty smell coming from my portable air conditioner?

  • It’s possible that mold or mildew has started to grow in your portable AC’s water tank.
    • Drain the water from the water tank. Then, clean it out with warm water and mild detergent, ensuring it’s completely clean and slime-free.
    • Rinse the tank with clean water, drain it again, and refill.
  • The condensate drain line could have algae or mold growth.
    • First, empty the water tank to prevent any water from accidentally draining out of the air conditioner while the drain line is removed. Remove the drain line by slowly pulling it off the drain spout. Then, clean the line by running water through it to remove any built-up grime.


Remember that when facing performance issues with your portable air conditioner, your number one resource is the unit’s user manual. You should contact the manufacturer’s customer service department if you have any other questions.

Any questions?

My Home Climate is your source for home comfort products and air cooling solutions. If you have any feedback or questions you’d like us to address, please get in touch with us at, where you can suggest topics for our next Air Comfort Answers blog. We’d love to hear from you!

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