F08
Ariston
Heater Relay Stuck On / Water Level and Heating Conflict
Machine fills and drains repeatedly without progressing; F08 error appears.
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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
Heater relay stuck closed on control board, shorted heater to earth, pressure switch misreading water level, wiring short between heater and control
How to Fix / Troubleshooting
Safety: Unplug immediately; a stuck heater relay can overheat the tub.
Steps:
- Insulation test: With the heater disconnected, use a megohmmeter (if available) to test resistance between each heater terminal and earth. Any reading significantly below 1 MΩ indicates insulation failure; replace the heater.
- Check pressure switch: Ensure the pressure switch and hose are clean and functioning (see F04). Incorrect level detection can trigger F08.
- Inspect control board: Look for welded heater relay contacts or burn marks near the heater control section. If the relay is stuck closed, the board must be replaced.
- Wiring check: Inspect heater wiring for damage or shorts to chassis.
Warning: Do not operate the machine until the cause of F08 is resolved; risk of overheating and fire.
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Repair Difficulty
Professional Required
5/5
Required Part
Main Control Board (Power Module)
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