Hello all,

Please could someone help me, I have a Worcester Bosch 24CDI combi boiler and a Mira 415 mixer shower, I have just come back from a weeks holiday and when you turn the shower on it goes hot then goes luke warm back to hot, I have watched the boiler when this happens and the hot water demand light stays on but for some reason the pilot light goes off and then starts back up again, it repeats this every other minute or so. It only happens with the shower it doesn't seem to happen with the warm bath tap or any other hot water tap.

The pressure on the boiler is 1 bar at rest.

What do you think it could be and how can I rectify the problem?

Many thanks

Mark

Hi

The gauge on the boiler measures the system pressure (heating) and is not connected to the hot water at the taps.

Could be just the valve needs a service, check the rose is clean and all the holes are clear, also lower the hand set to see if it makes any difference.

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if the shower rose isnt blocked, it could be that the inner rubber liner of the shower flex is failing.

The Mira 415 is a pressure balancing valve and it could be that the valve is a bit sticky causing a bounce between hot and cold. It depends how long the valve has been installed but you may need a service kit. Try all the other ideas first though.

Have a look http://www.showerright.co.uk/mira_415_s ... m_show.htm

http://showerdoc.co.uk/shower-spares/mira/mira-415.htm

Hope this helps

DWD

Does it happen on another hot tap if you run it slowly?

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Dave

www.drlgas.co.uk

Hi,

Thanks for all of your answers.

I have tried this on another tap at low flow and they work fine, the hot water comes out and stays like it.

As far as I know the shower is the original one in the house and has never had a service, so I am thinking it could be that, it's about 10 years old.

I have taken the cartidge out and looked at it, when you blow on the cold water side the ball inside moves on the pressure allowing a flow through but when I tried it on the hot side it didn't move but you can move it by pressing a needle against it and it doesn't take much force..

Is this normal?

I think that would be it....try a call to Mira technical advice line. They will be able to tell you if you need a cartridge or repair kit.

DWD

Hi all,

I have bought the 902.55 black cartirdge for the shower, fitted it and it has made no difference at all, so it must be the boiler...

I have booked an engineer to have a look tomorrow.

How can it be the boiler, if the other outlets are fine.

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I would go for the plate HE blocked on the system side, which was what my previous question was pointing to.

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Dave

www.drlgas.co.uk

if the other taps are ok at low flow, as said it cant be the boiler

did you check the hose?

let us know what engineer finds please.

Hi all

Well I have had the engineer in and it appears to be the diverter valve in the boiler, he proved it with a screwdriver, there appears to be a pin that it popping up and down when it shouldn't.

So I am just awaiting a price then we can ponder on either going for the repair or new boiler..

Does it pop up and down when other outlets are used.

I still say the problem is the valve, possibly backflow.

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Hi

It is really weird it only does it with the shower, I have cleaned the shower out replaced the hose and cartridge and still it does it the only time it didn't is when the engineer proved it with the boiler.