Hi

It could be a couple of things but check this out first.

It may be your solenoid valve, you can check it if you have a multi meter, you should have a reading of at least k3.5 ohms, across the two terminals any less and you need a new valve. (Check the valve in the failed state.) (When it is not working!)

If there is power getting to the solenoid and it is not operating then there is a good chance that you have a faulty solenoid.

If you don’t have a multimeter we sell them with a guide on how to use them for checking and testing the various parts of your shower.

Apart from helping to fix your shower, they are really useful for checking you have a power supply to appliances, for checking fuses and letting you know much power you have left in batteries

(So you will know if they are good or not) and lots of other jobs, in short they are well worth a few pounds

http://www.showerdoc.com/installation/electrical-products/SKYTRO-600-005-Digital-Multi-Tester

If it is completely cold then you may have a faulty Thermal Cut Out

A faulty TCO will have no continuity across the two terminals (The black thing on top of the heating tank)

Therefore a good TCO will have power at both connections and a faulty TCO will have power at only one.

(The function of the TCO is, if the water over heats it cuts the power off to the elements)

Check this out.

http://www.youtube.com/user/showerdoc#p/u/2/_zi8JbEMYMs

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 device will turn
the power off until it cools Then it all starts again

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


Also as it is a Triton have a look at the outlet TCO

The outlet Thermal Cut Out this is a black disk with two wires going to it and it is mounted on the out let pipe (The bit between the heating tank and the hose)
Examine the connections closely if you see any discoloration / signs of overheating then the TCO needs replaced.