Shower only produces extreme temperatures

[Jupiter01]

I have a Triton Cara electric shower and have an issue where the water is either very hot or very cold. When I turn the temperature dial it only oscillates between these two extremities.

I was planning to replace it but thought I'd check on whether it was a known issue. Thanks in advance.

 

[terryplumb]

The lower dial controls the water flow ,so turning clockwise reduces flow and temperature will increase ,and vice versa. So if you turn it ,slightly ,the temp rise should be slight. What do you get when you do this ?

 

[Diver Fred]

Sounds like the cold water supply to the shower unit is restricted so you only get a 'trickle' rather than a full flow. Do you have any form of turning off the water to the unit it's self? (Ball valve/Gate Valve/stopcock/appliance valve?) If so make sure it can allow a 'full' flow to the shower unit - 'Ball valves' in particular are notorious for not opening or closing properly.

 

[Jupiter01]

Thanks guys.
I do have an isloation valve and can check that again although flow seems to be "normal".
When I turn the dial slightly, there is no discernible difference in temperature. If I keep going, eventually it becomes scalding hot. There is no in-between. This was not the case previously.

 

[Hot&Cold]

Have a look at the faq's here,particularly #4 https://www.showerdoc.com/triton-cara-electric-shower-shower-spares

Showerdoctor,a very helpful company always my first choice for spares and advice

 

[John D v2.0]

Must be overheating if it really hits scalding hot. Agree with the restriction in the water supply or the shower head, but enough water to take away the heat. Make sure the hose is not blocked.
However if it was that then it wouldn't be affected by the dial which is what confused me. The other option is the heat element is scaled up or otherwise ineffective.

 

[seco services]

Suspect stabiliser valve fault.

 

[koomber]

Some showers have a filter which can get clogged with gunk gun can reduce the flow.

We had a similar experience with our electric which was due to the pressure reduction valve on the hot water tank being sticky (the cold to the shower was from this supply).

We ended up replacing the pressure reduction valve during our bathroom renovation (plumber did it as you must be certified to work on invented cylinders). However we got round the problem for years by turning the shower on, set to the lowest temperature then opening and closing a tap on the sink which was on the same supply. This seemed to open the prv enough to unstick it and get everything moving.