Boilermate 2000 no hot water

Called out to look at a no hot water problem last week on a Boilermate 2000, Only works on emergency, no display on the ACB, replaced the board and it all started working , 2 hrs later it's up to 75 and still not hot water, But hearing works fine. checked the hot water pump no power coming down bottom dash on in the display, no HER messages on display, linked pump and the hot water works great, shut down power to test electrics checked all pumps and had an OHMs reading of 500 on the water pump but only 190-200 on the other two. Turn the power on to test ACB board to pump live from the board (red wire) it goes up to the changeover switch no power from board, if I disconnect the wire from the connection on the board I get around 60v ? Don't wont to give up can anybody help ?

Sounds like loose connection.
Or faulty board
Mike

I did replace the ACB board the next day and still the same, I had the meter on the wiring from pump live to the ACB, Not at any point did I get more than 60v at the pump connection, have you ever changed the switch control PCB at the top ? Heating works fine and hot water works in the back up,

Hot water on the back up is not really related.
But the switch PCB could be.

I couldn't believe it two new faulty ACB's, finally with the third new board up and running, this caused me a major cause that I have tested it correctly, I think I can say I'm now an expert in Boilermate 2000

Well we all get one.
Faulty PCB's
Handled with gloves?
Static will take them out.
Mike