Unit shows E21; often related to drain pump-equipped Toshiba cassette or ducted units.

Safety first: Turn off power and be prepared for water spillage when opening drain sections.

• Step 1 – Check drain pan: Remove the indoor panel and inspect the condensate pan. If full of water, the pump or drain line is likely blocked.
• Step 2 – Clear drain line: Use a wet/dry vacuum at the drain outlet to suck out clogs. Flush with water to confirm free flow.
• Step 3 – Inspect pump and float: Locate the drain pump and float switch. Clean any slime or debris that may prevent the float from moving freely.
• Step 4 – Test pump operation: With power restored, pour water into the pan and observe if the pump activates and drains water. If not, check the pump connector and replace the pump if silent or weak.
• Step 5 – Replace float switch if faulty: If the pump runs but E21 persists, the float switch may be stuck or defective and should be replaced.