My H.P. R65 Officejet printer has scanner fault?

This generally reliable 'All in one ' printer now has developed a coying/scanning fault.

The 'Warming up' stage in the copy process seems to have become extended and after two minutes the machine cuts out and displays "Scanner system failure, Turn power off then on aagain"

Presumably the relevant heater is failing or has become disconnected.
there are no obvious faults in the scanner trolly so I assume that it is the fuser heater that is at fault.

Can anybody please help?