Faulty Myson MPE322?

1 Dec 2021
Reaction score
United Kingdom
Earlier today when calling for heat (measured with multimeter, 240v on call wire). Sounds like it's stuck and not sure why both LEDs are on.

Later on today calling for heat is doing absolutely nothing at all. Still high voltage on line.

Hot water seems to be working fine. Drayton LP522 and nest heat link used with same results. Boiler is a potterton promax sl
Sponsored Links
The lights indicate which port is open, so for both ports to be open, the valve should be in the mid position supplying both hot water and heating.

Here's a 3-Port valve test procedure. OK it's for a Honeywell valve, but the wiring connections should be the same as yours. If you get the readings shown and the valve doesn't behave as described then it's faulty.

3-Port Valve How to Test.jpeg

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links