Shower pump won’t turn off.

[grommett]

I’ve been running a grundfoss neg head whole house pump for a number of years with no problem until recently. When a tap or shower is turned off the pump continues to run. I thought I would try and diagnose without removing the pump. Firstly I shut off both outlets to eliminate leaks in the pipework. Then I checked the switches by disconnecting the pressure switches and flow switches from the controller and shorting the connections to emulate open and closed switches. None of the combinations I tried made any difference. I am starting to think it is the control board but I would have thought a faulty board would cause the pump not to run at all?
Getting a bit stumped now.

 

[trojanhawrs]

Take a picture of the control board

 

[grommett]

 

[trojanhawrs]

Firstly, check for continuity between the live and motor pins in case the relay is stuck in.
I take it you have a suction side and discharge side switch pressure switch? I'd assume with the suction side disconnected it shouldn't want to run.