Coway airmega 400 filter reset

The letters on the [Pre Wash] button are lit. The pre-filters need cleaning. On the 400S and 400 the button also shows the pre-filter cleaning cycle in levels from 100% down to 0%.

Cause 1 of 2The pre-filter cleaning cycle has run out, about 2 weeks at 8 hours a day at maximum speed. Source: Checking the product; Filter Maintenance and Cleaning Parts; Pre-filter, pp. 10, 19–20

First checkClean both pre-filters.

Causes and checks

The pre-filter cleaning cycle has run out, about 2 weeks at 8 hours a day at maximum speed. Source: Checking the product; Filter Maintenance and Cleaning Parts; Pre-filter, pp. 10, 19–20
1. Clean both pre-filters. See Clean the pre-filters.
2. Touch and hold the [Pre Wash] button for 2 to 3 seconds to reset the indicator.
The cleaning cycle was not reset after cleaning the pre-filters. Source: Pre-filter, p. 20
1. Touch and hold the [Pre Wash] button on the control panel to reset the indicator. The cleaning cycle must be reset after every cleaning.

Service

If the checks above do not clear it, contact Coway customer service: 1-800-285-0982, cowaymega.com. United States (warranty service, 8:00 am to 5:00 pm PT, Monday to Friday). Source: Limited Warranty, p. 28

Other Airmega 400 indicators

[Max2 Change] indicator: The Max2 filters need replacing. On the 400S and 400 the button also shows the filter life in levels from 100% down to 0%.
Wi-Fi indicator: Wi-Fi connection state of the Airmega 400S and 300S.
Air quality indicator colour: Pollution level around the purifier. 400S and 300S: blue and green is Good, green and yellow Moderate, yellow and pink Unhealthy, pink and red Very Unhealthy. 400 and 300: blue is Good, purple Moderate, pink Unhealthy, red Very Unhealthy.

Sources

User Manual, Air Purifier 400S/400/300S/300 (English, French). Coway. Document 1216776, revision 003, 88 pages, en-US. cowaymega.com. Listed on the manufacturer's support page. Retrieved 13 November 2026.

Page numbers are the numbers printed in the manual. Where this page and the manual differ, follow the manual.

Applies to: AP-2015E (variant AP-2015E(SILVER_US)), AP-2015F (variant AP-2015F(SILVER_US)), AP-1515G, AP-1515H. United States.
Source: User Manual, Air Purifier 400S/400/300S/300 (English, French), 1216776 revision 003
Last verified: 13 November 2026
Handbook: Coway Airmega 400S, 400, 300S and 300 air purifiers in Air purifiers; all Coway handbooks