Stuart Turner powershower pump control modules

[Hugh2011]

I have a Stuart Turner Showermate 1.4 bar twin pump for my powershower.
There are two control modules attached by screws to the outsides of the pump on the connectors to the water pipes feeding my shower, one for the hot water side and the other for the cold water side.
The shower will now only provide powered cold water. If I switch the control modules around, the shower will only provide hot water. So I need to replace the failing control module.
I thought the control modules were electromagnets that operated reed switches inside the pump but they could instead be sensors.
How do these control modules work?

Also the price Stuart Turner wants for replacement control modules seems high for what they do.
Thee a labelled HAMLIN RP 357-15 00916 but I contacted HAMLIN and they do not recognise them.
Can I get replacements more cheaply than from Stuart Turner and where please?

 

[picasso]

The reed switch is strapped to the outside of the pump, when you open a tap the flow pushes a magnet near the switch which brings the pump on, how much are stuart and turner asking for a switch ?

 

[Hugh2011]

The reed switch is strapped to the outside of the pump, when you open a tap the flow pushes a magnet near the switch which brings the pump on, how much are stuart and turner asking for a switch ?

Thanks.

When I touch the switch with a magnet the pump comes on but I still only get powered cold water. Maybe the magnet inside the pump has lost its magnetism because it lives in very hot water. If I swap the switches cold<-> hot side I get powered hot water. That seems contradictory to loss of magnetism. So more diagnosis to do.

A pair of switches from Stuart Turner is £30 plus VAT & postage.
(What for simple magnetic reed switches?).

The pump is 8 years old and even if I sort out the current problem there may be further failures soon.

Ouch! it may be time to buy a new pump by this tightwad pensioner.