hard water

If you have a low pressure light on an Opal

 The first things to check 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 the pressure switch therefore no power will get to the elements

and the unit will show low pressure.

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

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

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

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