flow and primary sensor?

[Ian69]

Potterton Performer 28. low temp on my DHW. I need to turn hot water full on to see the micro switch activate and then the water is only lukewarm. was told by a plumber that it was the above (flow and primary sensor). P.T.S have checked their stocks and have no idea what they are!! Could it be the micro switches that are fecked??
Thanks

 

[TCCHeating]

Sounds like you need a new diaphragm, probably worn or a hole in it

 

[ianmcd]

TCCH has just given you the correct advice without even seeing your boiler, hope you didnt actually pay the so called engineer who told you absolute crap

 

[Ian69]

thanks fellas! The engineer didn't charge for the info Ian. to be fair he also mentioned the diverter valve diaphragm but said the sensors or whatever they are would be cheap to buy and might solve the prob!