Glow Worm 24cxi hot water problem

[Call4heat]

Hope someone can help?
I was called out to this breakdown today (just started boiler breakdowns after 12 years of installing)!
Symptoms... CH flow pipe heats when any hot water outlet is opened.
Only 1 hot water outlet (kitchen sink, closest to boiler) operates at a constant temperature, bathroom hot water outlets fluctuate in temperature!
I thought it could only be 1 thing, diverter valve!
I removed the motor from the valve and checked for correct movement of spindle which was fine
So I went off and purchased a spindle repair kit and replaced the existing which was scaled up and covered in black deposits!
The replacement was not easy as the installers had not left the correct clearances around the boiler which meant I could not remove the left-hand panel!
But I eventually managed to replace it, commissioned the boiler but the same problem occurred!
Thinking that I may have installed it wrong, I removed it and re-installed it, BUT annoyingly the same problems are arising!

I would appreciate any ideas/feed back please!
I have heard that a DHW heat exchange that is blocked can cause the diverter valve to not sit back to it's correct position and cause the CH flow pipe to heat up when the DHW is drawn!

Many thanks,
Mark.

 

[entreri911]

hows the diverter motor? i have had a few of them constantly motoring back and forth which causes the symptoms you have described. it especially effects the hw as it runs hot then lookwarm/cold constantly.

 

[Call4heat]

Thanks for your reply!
I have checked the motor, it works as it should and moves correctly on demand.
Could the P-HEX, if blocked cause excessive pressure from the pump causing the seating on the spindle of the diverter valve to lift and cause the CH flow pipe to heat-up?
Can anyone confirm or experienced this posibilty?

Thank you in advance!
Mark.