wen i turn the hot water tap on it only gets warm ?

just changed divertor valve and actuator on my central heating and same problem still exists. I have a combi boiler oil fired (heatslave 20/25). System has been bled but unless i switch off thermostatic radiator valves rads get hot when only HW turned on (i.e CH in off position) We didn't have any HW or Ch before I changed the divertor assembly, so that has at least been cured. Not sure why Ch comes on aswell wtih HW only. Possibly faulty programmer or other valve? any help appreciated

Hendy
September 2008