Mira Sport Shower - Flow problem?

[kma2k]

Hi - first post here so hello!
We've got 2 Mira sport showers in the house and have replaced them pretty regularly over the last few years - generally seem to last for 3 years or so before something goes wrong and its often been cheaper to get a new replacement off ebay than call out Mira or replace parts at random. Previously the low pressure lights have come on and there's been no control over temperature.
This time, the shower doesn't show any low flow light, but makes a lot of noise as though the water flow is trying to get through a restricted opening. The flow at the shower head is drastically reduced to not much more than a dribble.
I've tried running it on the cold setting for a few minutes without the hose attached, but the flow rate doesn't change.
Turning the temperature knob doesn't seem to make any difference to flow rate (expected it to be higher flow on a cold setting) or the temperature. The temperature stays cold throughout.
I then tried taking out the filter and found tiny bits of grit/ debris but no obstruction to the flow at all. On re installing the filter and switching the water back on, it worked as normal! Lots of flow, and heat.
Great, but after switching the shower unit off and then back on, we're back to square 1 - noise and low flow at the shower head.

Question is, does this sound like a flow valve problem? I don't want to order the wrong part at £40-£50 if i can help it Are there other checks I should be trying? any help gratefully received!
The heater tank looks like it was made 2011 /09 which makes it 3 years old.

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[ALCPlumbing]

What's it like through the hose only with the shower head taken off. Had this before and it was a scaled up shower head causing the restriction.

 

[kma2k]

Hi, I've just gone and tried that but its the same as with the hose off completely. Putting my thumb over the end it does build up pressure and it sounds like the heater tank is filling up as the pressure builds, but its still cold water, no temperature change as I moved the dial around.

 

[kma2k]

To add a bit more, I've got a multimeter and measured across the two solenoid contacts and got 3.9 ohms, which from reading other posts appears to be in the right range.

Does anyone know which contacts to measure across for resistance on the heater elements? obviously I've got the power supply off while I'm doing this.....

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[leakydave]

Isolate the water supply and undo the black nut that houses the filter... it could be bunged up.

 

[kma2k]

Hi Dave, tried that earlier,

[/quote]I then tried taking out the filter and found tiny bits of grit/ debris but no obstruction to the flow at all. On re installing the filter and switching the water back on, it worked as normal! Lots of flow, and heat.
Great, but after switching the shower unit off and then back on, we're back to square 1 - noise and low flow at the shower head.

but no luck - same old problem.

 

[seco services]

flow valves faulty.

 

[kma2k]

Thanks, is it worth me doing any more checks to eliminate other parts?

I've now measured the ohms between the blue neutral connection and each of the other element posts and get 13 ohms, so if the heater is OK and the solenoid, I suppose all it can be is the flow regulator?

If t was a broken microswitch I guess I would see only one element working in the heater when it was working?

 

[kma2k]

Just to close this thread, i fitted a flow regulator valve tonight, took about 20 minutes and sorted the problem

It might hep other people to identify issues they are having....