Electric shower fault

[cj66]

We have two electric shower units with exactly the same problem but I'm lost on diagnosing the fault(s) i.e. cold water and no power light. One is a Sharp, the other a Mex.

Tried so far;

>Checked gauze filters.....clear.
>Set to low temp., lower head and turn unit on & off min. of ten times, then raise head, use high temp and turn on again.....no change.
>Runs same water flow with or without head.
>ECB switch running correctly.
>Power is reaching unit.
>Water pressure is good.

WITH POWER DISCONNECTED;
TCO has continuity.
Heater reads 18ohms across terminals.

There remains the the water flow sensor to be tested but I don't know how you do that. Any of our clever bods here have more ideas?

(Wasn't sure whether to put this post here or in DIY)

 

[a.palfreyman]

Do you mean an electrically heated shower? I think but not certain that these require a min mains pressure to function. I'm not aware of them having a 'flow sensor' as such. Only ever come across these in electric shower pumps (for mixer showers) and these are normally fitted with reed switches to detect water flow.
https://temperaturemaster.com/electric-shower-not-getting-hot/
This explains about testing the TCO

 

[Darth Vader]

"no power light" means just that no power for the heating element. Is there a heater trip? This is usually a small bit of metal rod that protrudes outside the tank and disconnects the power within the heating element. Immersion heaters have these and they can trip for several reasons. If you find one give it a good press until it clicks in place. Its just a guess as I've never had one of these but does fit the scenario.

Cheers,

DV

 

[wow&flutter]

The two main items to check are the thermal cut out ( usually strapped to the cylinder) and will have one wire in/out which cuts the power if the drum overheats. Second item is a sensor on the water input that checks water flow before allowing it to switch on electrically. The thermal cut out was a favourite for packing in back in the day especially on cheaper units.
More complex units may have additional electronics but will still likely rely on the two items I’ve mentioned. With a meter it should be quite easy to determine if they are allowing current to pass.
I’ve no idea what the heating element resistance should be so can’t comment on that unfortunately.

 

[Ian G]

18 ohms sounds to high for an electric shower, less than 3kW at 240v

 

[cj66]

Thanks all,

I have checked over the little control board for dry joints or any other visual irregularities.

@a.palfreyman
Yes, I found that same link.

@Darth Vader
No luck on that, not present in these designs.

@wow&flutter
Agreed.

@Ian G
3.5kw & 18ohm is, apparently, in the healthy range.

 

[davidsrsb]

My instant showers have a power light and a heater light. The power light is on so long as the wall switch is on. The heater light can only come on when there is water flow

 

[Mike P]

I found the youtube videos from here to be very helpful.

https://www.showerdoc.com/blog/electric-shower-problems-5-most-common-faults-and-what-causes-them

My problem turned out to be a faulty solenoid valve.

 

[Ellenor]

Never heard of any of those showers. They’re probably cheap ones and the cheap ones usually don’t last long. By the time you source spares and repair them you’d be better off just replacing them and be done with it.

 

[cj66]

@Mike P
Yup! The older Mex one also has a faulty solenoid
Newer Sharp one still a mystery. Found a test for the water flow sensor, passed. Grrrrr. Have fitted a new Toshiba but if I can fix the Sharp as a spare it would be handy.

@Ellenor
Very much the norm here, can get more powerful but have to be sure the power rating matches supply
New solenoid ordered for the princely sum of £2.