Worcester combi heatslave 15-19 oil boiler no hot water only when i do some fiddling about with the controls!
we have changed diverter valve and replaced the electric timer but still no hot water.
if i fiddle with the temperature control knob it sometimes gives me hot water but doesnt always click when i am turning it. is it as simple as that that i need to replace the control knob and possibly the thetmostat box behind it or is it a more complex fault

Lizzie, December 2011

im an oftec engineer.
your boilers water temp thermostat is faulty by the sound of it, and is available at any heating spares supplier. it comes with a capillary tube with sensor bulb, and the thermostat body. it has one nut behind the green dail (that pulls off) holding it in place, and insulated wire terminals pushed onto the spades on the rear of it.
simple job for an engineer.
Also get someone to run a hot tap, and listen for a definite 'click ' from the boiler as the tap is turned on/off...if no click, the flow switch is sticking.

mark properjob, February 2012