Richardmerri wrote:
Hello all... My Honeywell ST799 Programmer is problematic! I can no longer use HOT WATER alone, but only the CENTRAL HEATING programme switches on the boiler. Also, when I attempt to programme in the time for either the HOT WATER OR CENTRAL HEATING the times change for both simultaneously! Has anyone else come across this 'delinquent' behaviour? Or can anyone suggest a fix? Any advice will be much appreciated... Richard.

It has possibly got its knickers in a twist.
Remove the battery and short the terminals in the programmer to
discharge any capacitors. replace battery and reprogramme.

Might work?