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Errors


Boiler type Mod con 850

Error code F03

Cause:

Interrupted or shorted return (inlet) thermistor.

Solution:

- Check the electrical connection to the appropriate thermistor. Verify 5 VDC by checking in Molex connector. If not 5 VDC, check harness. If harness is OK, replace control. NOTE: Boiler will reset automatically. Verify thermistor values by referencing chart in this manual. 
- If connection is okay, replace thermistor.