Fixing Non-stop Running Fault on Generic Shower Pump from B&Q

The visiting daughter seemed to be spending a long time in the shower, as the pump motor ran and ran... However, she then appeared downstairs, and suggested that there may be something wrong with it, as she'd turned it off and the motor was still running! Damn. With her spouse and the g-kids also staying, it could be a problem. First stop, press the "test" button on the in-circuit RCD to kill the power...

View of shower pump showing location of flow sensor
View of pump, pointing to one of the two sensors

I already realised that the pump turns on when the state of the water in the output lines changes, pressure, flow, whatever. Some Googling revealed that equivalent 3bar pumps are not cheap! So just buying one and replacing it myself was financially not the first option. So - repair? A photo of the inline switches revealed the text "HAMLIN 59600-444". Hamlin apparently make reed switches, and although I'd not really given much thought to how the pressure/flow switches might work, this seemed pretty reasonable. Nobody had one for sale though. By the way, a Positive pressure pump works on flow, and a Negative pressure pump work on pressure. I think mine's Positive.

HAMLIN clamp-on reed switch 59600-444
One of the reed switches showing part info

But one Grundfos spares site did have a repair kit, with a different looking Hamlin part, and a question asking if it was a suitable replacement for mine, answered with the correct but useless response that the part was for the specified pump, so if you had one of those, it was correct. Thanks.

More Googling found a response on the Screwfix forum to someone asking about a similar situation for a customer, and a response that using a magnet to jiggle the part inside the pipe and to jiggle the reed switch around could possibly work, with success reported by the original poster. Let's try it...

Initially I tried just using some strong magnets, waved around the switches. This had no effect, rather disappointingly. So I removed one of the switches (the left hand (cold flow) one in the picture), tapped it against the pump body, waved the magnet around it, and also rubber the magnet up and down, all around, the copper "tower" onto which the switch is clamped. Replaced the switch on the pipe. Tried the RCD - result! And I'm happy to report that the pump didn't cut in, and we've had a number of showers since and the pump has stopped as per requirements. 

Wonderful. And of course, I look like a plumbing wizard to the grateful throng.

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