What F78 Means
F78 means the condensation drain path on a condenser or heat-pump dryer is blocked or not draining properly, causing condensate water to back up instead of routing to the collection container or household drain.
Common Causes of F78
- Lint buildup blocking the condensate drain path
- Kinked or clogged condensate drain hose
- Failed condensate pump
🔧 One Safe Check You Can Try
Empty and rinse the condensate container if your model uses one, and check that any drain hose (on models plumbed directly to a household drain) isn't kinked.
⚠ Why You Shouldn't Go Further Than That
- If emptying and rinsing the condensate container doesn't clear it, the blockage is further into the drain path or the pump has failed, which needs internal access to confirm.
- A failed condensate pump involves both water and an electrical connection, making a live test risky without disconnecting power first.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.
Technical Reference
- Code
- F78
- Appliance
- Miele dryer
- Maker documentation
- Miele owner manuals and use & care guides
- Checked
- September 2026
Code meanings can change between control generations. Before acting on a code, match the full model number on your appliance's rating label against the manual for that model. We are an independent repair service, not affiliated with Miele & Cie. KG.