Hi Lads, thanks for replying.
Checked all voltages all ok on 3 port v/v.
When first fitted only hot water was supplied all ok.
Then call for heating all ok.
Then when HW calling valve is staying in mid position.
Why would programmer be at fault?
Customer said worked ok I only fitted 3...
System y plan but megaflo unvented cylinder controlled by 2 port v/v.
Fitted new 3 port mid position v/v rads still getting hot when HW calling only.
Why this system has a 3port v/v instead of 2 off 2port v/vs I dont know.
Any suggestions.
Many thanks, John.