Frequently Asked Questions
Why does the light on my C-90 blink or flicker?
The light will blink/flicker due to the fact that it is a neon gas bulb, which is reactive to humidity, temperature, etc. This is normal, and it might be intermittent.

Some users have reported a rhythmically flashing bulb (on beat) which could be indicative of an electrical issue in the installation or that the unit may need to be cleaned, as the light is meant to stay on when the cell is in place, and the contacts are made between the cell and the unit’s power board.

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• What is the difference between the Friedrich C-90B and the Friedrich C-90A?

• Why does the light on my C-90 blink or flicker?

• Is the C-90B effective against mold?

• Does the C-90B electronic air cleaner produce any ozone?

• How can I buy replacement carbon filters?

• How often should I replace my carbon filter?

• Do I need to replace my pre-filter?

• Where do I get filters for my C-90A or C-90?

• How do I find a Friedrich dealer in my area?

• Where can I download an Owner's Manual?

• What are the Friedrich C-90B's dimensions?

• How often should I replace the carbon filter in my Friedrich air cleaner?

• How quiet is the Friedrich C-90B?

• Aren't the filters really expensive?

• How large an area will the Friedrich C-90B handle?

• Will the Friedrich C-90B discolor walls, drapes or furniture?

• How do I know which air cleaners are really effective?

• How much electricity does the Friedrich C-90B air cleaner require?

• How do I clean my Friedrich air cleaner?

• How do I install a carbon filter on my electronic air cleaner?

• Can I use my Friedrich C-90B with my window open?

• Why is my electronic air cleaner making a popping sound?

• Are there discounts for purchasing more than one Friedrich C-90B?