F66
Miele
Heater Relay Stuck / Safety Monitoring Fault
Dryer shows F66 and may not heat or may stop.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Stuck heater relay contacts, welded relay due to surge, control board logic fault
How to Fix / Troubleshooting
Safety first: Unplug the dryer. Do not operate a dryer with a suspected stuck heater relay due to fire risk.
Check heater control:
- Access the main control board and locate the heater relay.
- Inspect for signs of overheating or melted plastic around the relay.
- With the dryer unplugged, test continuity across the relay contacts; they should be open when not energized.
- If the relay is stuck closed or visibly damaged, the control board should be replaced or professionally repaired.
- After replacement, verify that the heater cycles on and off correctly during operation.
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Repair Difficulty
Professional Required
5/5
Required Part
Main Control Board (Heater Relay)
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