pressure light

The things to check first are.

1 That the main valve coming into your house is fully open.

2 Then check that the valve on the line to the shower is fully open.

If these valves are not fully open then there may not be enough water
getting to your shower to open / close the safety device that allowspower through to the elements

 The first things to check are:

1  That the main valve coming into your house is fullyopen.

2  Then check that the valve on the line to the shower isfully open.

If these valves are not fully open then there may not be enoughwater

getting to your shower to open the pressure switch therefore nopower will get to the elements

and the unit will show lowpressure.

Forgetting about the temperature turn the shower from fully hotto fully cold at fully hot you should have not much more than a dribble comingfrom the hose and on fully cold you should have a good strong flow, if you donot have this difference then you may have a faulty flow/stabilizer  valve

Finally when you turn thewater on, the top of the flow valve should rise, there is a plastic actuator ontop of the valve this should press against a micro switch at the bottom of thePCB make sure they are properly aligned.

If all these are OK then youprobably have a fault with your PCB.

The checks don’t guarantee that you have a faulty power PCBhowever they do eliminate just about every thing that could cause the lowpressure fault and so the only thing left is the PCB.