Decided to give our electric shower unit a flush out today. Just a basic cheap on the wall job. I (probably stupidly) reversed the input water to back flush it and now not working. I'm guessing I may have damaged the flow switch? I see there's a small sensor with three wires on the pipe. Maybe combined thermostat / flow switch. I gave it a tap but no joy. Anyone have any ideas?

What is not working? The heater? The water flow?

The waters flowing.

No power light / heater.

Earth trip switch ok.

Water connected correctly

Have no idea how made but suspect you are right but you should have power light even without flow switch activated I suspect. The ELCB is tripping with button press? That would indicate power through the main breaker but with no power light wonder if some electronics got wet and may dry out. Hair dryer handy?

Have no idea how made but suspect you are right but you should have power light even without flow switch activated I suspect. The ELCB is tripping with button press? That would indicate power through the main breaker but with no power light wonder if some electronics got wet and may dry out. Hair dryer handy?

Nothing got wet and the RCD is tripping. Power light will only come on if sufficient water flow. The water flow is also strong.

As stated I ran the water backward through the unit to flush. I guess I have damage the flow switch paddle or something

Sounds correct - but believe some of my units had power light indication without it meaning any heat or water flow - guess different units are different. Although they can probably fix might be faster and not much more expensive to buy a new unit. I have had good luck with the inexpensive Panasonic units - much better water flow than most others and very water tight.

SWITCH OFF THE POWER AT THE MAIN BREAKER

Remove the bit you think is the offending part part ensure it is all free and reassemble, normally a reed switch or a bobbin.

+1 on sappersrest's suggestion, probably reversing the flow has caused the flow switch to get stuck (possibly with a bit of gunge that got dislodged).

Dismember and clean carefully.

Or buy a new shower unit.

+1 on sappersrest's suggestion, probably reversing the flow has caused the flow switch to get stuck (possibly with a bit of gunge that got dislodged).

Dismember and clean carefully.

Or buy a new shower unit.

looks like an external switch or sensor. Can't see anything like a paddle etc going into the pipe. Will have a better look today. What do they normally have Crossy? Is it a thermostat / flow switch combined?

It depends upon the heater type, some have a pressure operated switch some a flow switch. Turning it upside down and giving it a thump on the bench may free it.

A thought, you did try it with the shower head fitted didn't you? If it's a pressure switch it may not have had enough back-pressure to trigger.

It depends upon the heater type, some have a pressure operated switch some a flow switch. Turning it upside down and giving it a thump on the bench may free it.

A thought, you did try it with the shower head fitted didn't you? If it's a pressure switch it may not have had enough back-pressure to trigger.

just pulled it apart now. Little hinged magnet inside with a prox sensor on the outside. If it was stuck it's operating now but heat light still not coming on. I can here the flow switch operating when i turn the water on and off. I did notice though I have no test lamp light between active and earth? The rcd is tripping ok. I didn't think the unit would function or rcd would trip with no earth?

Again ensure power is off, look out for a tiny push reset switch, maybe on the pcb if it has one, or on the thermostat it's self.

Turns out is was the external sensor / prox. The one the internal magnet operates. Must have just been a coincidence that it happened after I back flushed the unit. On second thought though, thats why I flushed it...even after turning the water off the heat light was staying on and coughing and spluttering because no flow but element still running. Anyway, 300 baht to replace and all running fine. Thanks all for the help