Observation:

Appliance has reset after fault code E13 occurred.
If appliance has been fitted with an additional sensor at the top of the heat exchanger then this is the most likely reason for the fault.
Check the seals around the burner / heat exchanger assembly, if they are faulty further investigation as to the cause will be required and safe operation of the appliance must be confirmed. A service kit with replacement seals is available under GC: 724-391
or alternatively refer to ADAPT to order individual seals.
If the seals appear satisfactory or this additional sensor is not fitted then choose option below:
USE FULL XSOL MODEL
INVESTIGATE POSSIBLE CAUSES OF OVERHEAT
If fault continues to occur then it is possible the fuse has deteriorated and requires replacement. It is not available as an individual spare part and would require a replacement heat exchanger so all other possible causes should be investigated first.