elecrta mate 2000 hot water problem

hi

was called out to the electramate for no service turned out to be no presure in expansion vessel and too much air in the radiators once these were sorted all was running

the other problem the customer had was that the hot water is not very hot
when i ran the hot water with a low flow rate it came out piping hot but once the tap was opened more fully it went cold
would i be right in thinking that the thermistors require changing
also i would suspect the plated heat exchanger is gunked up this too to be replaced or is there something im missing out !!

could someone coinfirm this please

I assume the unit is up to temperature.
It could be;
DHW sensor
PHE sensor
PHE scaled up
PHE pump
Blending valve
Have you the book?
If not down load one for free at Gledhill web site.
You can check the ACB to see if there are any sensor faults.
Mike
MGC/H2O
Norfolk