Worse when running heating as well as hot water. Have replaced control unit and solenoid but keeps occurring. Power light flickers - could it be something to do with power supply?
i would have the basic tuneup done parts 1,2,3=noz.,o.f.,p.s.,f.o.l.-flush oil line,check ing. transf. adj.electrols and so on,in otherwords have it serviced. also make it clear you have a reset problem.
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Try fixfault.com to fix home heating systems.