Temperature fluctuations

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 cool it properly, the overheat safety devicewill turn
the power off until it cools, then it then it starts to heat again andso on.

Make sure that the shower headis clean and clear, that the hose isn’t kinked (this can happen just behind thehand set where it is difficult to see) also check the inside of the hose althoughit can look OK on the outside it could have collapsed internally

The other possibility is a faulty flow/stabilizer valve not allowingthe correct amount of water into the shower.


Also have a look at the outlet TCO

The outlet Thermal Cut Out this is a black disk with two wires going toit and it is mounted on the out let pipe (The bit between the heating tank andthe hose)

Examine the connections closely if you see any discoloration / signs ofoverheating then the TCO needs replaced.