Valiant combo

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3 Jun 2005
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London
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United Kingdom
Not sure of exact model but my Hot water keeps going cold when I have a shower. It is ok when I use the taps but when I swicth the mixer to shower it goes cold. If I turn the shower on the heater does not fire-up ay all. But if I switch on the tap down stairs I get can use the shower for a few minutes. The problem started when I turnt the water of from the mains since then on-going problem. HELP!!!! Also get a whistle noise from shower.
 
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could be the hot water side of your shower is filled with muck. One assumes that you are using a bath tap /shower mixer tap?take off hose/shower head check flow and do the necessary
 
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It now seems that I have a turbo combi. If I turn up the Central heating I get hot water and to get the mixer shower to stay hot I have to keep the kitchen hot tap on! Confused you will be!
 
DOes it have a black panel behind a door, with green knobs on? If so it's an early Turbomax. It sounds like it has problems with the diaphragm/diverter valve, (which makes the boiler switch on , with heat directed to HW) and/or very likely sludge in the boiler side of the secondary heat exchanger (which transfers the heat from boiler water to tapwater).

They're both common problems. First means the boiler is slow to switch on for HW and you don't get much, second gives the on-off-on. New parts for both would be 250 ish, though some would clean/refurb, giving less certainty, and more labour.
 
It does have a black panel and green knobs. The problem started when I turned the water off and when I switched it back on the water pressure in the shower was lower and when I did get hot water as soon as I put cold in with it, it went cold.
 
DV won't be responsible for low flow - are you in a hard water area? Could it be limescale? Or the flow restrictor may have distorted itself. Best place for 'em is the bin anyway.
 
Check operation of diverter valve (bottom right) - on the side there is a small black electrical switch which should be operated by a lever extending from the diverter valve whenever water flows from hot taps. It may be that the shower flow is too low to activate the switch. However the switch angle can be adjusted to make it more or less responsive to low flows.

Do not attempt this without careful reference to Servicing Instructions (your boiler is Vaillant VUW 242 (or 282) possibly with E suffix). If you are not clear about what you are attempting, get in professional. Do not attempt anything more ambitious with diverter valve (e.g. new service kit) unless you really are competent - it's a difficult job with potential to do more damage to boiler.
 

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