Valliant Combi Prob: hot water goes cold when shower is on..

[August101]

Hi

I am hoping for some help here please, we have a Valliant combi boiler in our flat and about 4 weeks ago we noticed that the hot water in the bath/shower became intermittent.

I would be in the shower and the CH would be off, the water would come out hot then go stone cold. After leaving the tap off for a few mins (and covered in soap) the water would come back hot then go cold after 5 mins. This cycle would occur quite alot. The taps in the bathroom basin would do the same, the hot water would be flowing and then it would go to cold.

The Rad work fine, we have tried the hot water with and without the heating on, still the same problem. the pressure bar reads A.ok but the temperature gauge on the boiler doesn't move, its stuck in the black area at the bottom of the gauge.

Can anyone please help, we are in South London and would love to hear any solutions, if its something where we need some specialist advice then can anyone recommend a decent plumber?

Thanking anyone in advance

August101

 

[breezer]

you want a heating engineer, not a plumber

 

[kevplumb]

 

[kevplumb]

model of boiler might help

 

[PEDANTICVINDICTIVEMAN]

Have you tried jumping in the shower when it's hot, then jump out when it's cold, in out in out shake it all about and singing the okey kokey

 

[Bahco]

Nice one

 

[ChrisR]

There's nothing like being helpful, is there chaps, and ....

Common problem if there isn't enough flow for the boiler to control the water temp properly. Is it OK at the kitchen hot tap if you leave it on?

Suppose you leave a bathroom hot tap on while you're in the shower?

Sounds like the temp guage may be bust, which doesn't lead to other problems as such.

Usual cause is sludge/scale deposits in the system. Not a huge problem to fix - easier on some boilers than others. Is the boiler the one with the door which opens to the right to reveal a black panel with lurid green knobs?

Where in Sahf Lundin are you?