Hot water problems worcester 24 cdi

[jonbut]

I am having problems with hot water. when tap is turned on, hot water demand light comes on and get hot water for approx 30 secs, demand light goes off boiler cuts out and water goes cold for approx 20 secs, then starts again, on,off,on,off. the d/v switches across with little flow demand(assume d/v ok). seems to be an overheat problem? replaced temperatue sensors on gas to water h/e and below gas to water h/e l/h side below air vent. can anyone help me is this an obvious fault
jon

 

[corgiman]

diverter valve I reckon

 

[pannierstan]

Not so sure it would be unusual for the D/valve to act like that. I recon some thing to do with the micro switches on the end of the d/valve.
You really have to do some diagnostic checks with a meter

Stan