A104 Converter overtemperature fault in ABB DCS800 drive indicates that the converter section of the drive has exceeded its maximum allowable temperature limit. 

Troubleshooting Steps:

1. Wait until the converter is cooled down.
2. Verify that the motor load is within the drive's rated capacity.
3. Visually inspect the cooling fan for any obstructions or damage.
4. Ensure that the fan is spinning freely and efficiently.
5. Check that the drive is installed in a well-ventilated area, away from heat sources.