Baxi Combi Instant 105e HE - Hot Water Ok but NO CH

graemefarrer · 27 Sep 2010

Hi Everyone,

I really hope someone can help me.

I have a Baxi Combi Instant 105e HE which was working fine last winter, switched it over to hot water only for the summer months with no probs, but now wanting to put the central heating back on and it doesn't want to work.

The hot water still works fine its just the central heating isn't coming on. There are no fault lights lit, but also the green light that usually lights to tell you its in central heating mode does not light at all.

I first thought it might be the timer/override switch, however replaced that and still nothing. Bled the system and pump too, still no joy.

Any advise? Thanks in advance,
Graeme

powell30 · 27 Sep 2010

Never understood why people switch the boiler over to hw only......switch of timer and stat and it is......er hot water only delivery!

Probably stuck diverter......strip, clean or replace

graemefarrer · 27 Sep 2010

Thanks for your reply.

I thought that was what the selector switch was for, but if I had known it could cause probs like this then I would have just switched off the timer as you suggest.

So am I right in thinking that you think it is probably the central heating pressure differential valve rather than the domestic hot
water pressure differential valve, and that removing and refitting the diaphragm is all this needs?

Thanks again,
Graeme

adlplumbing · 27 Sep 2010

greamer if hot water works then try the time clock

petit_pablo · 27 Sep 2010

If the heating light isnt coming on then the boiler doesnt know there is a heating demand.

graemefarrer · 27 Sep 2010

I tried replacing the timer clock with a new one,
1st thing I did after reading about it in this forum,
but unfortunately this did not work.

graemefarrer · 27 Sep 2010

petit_pablo said:
If the heating light isnt coming on then the boiler doesnt know there is a heating demand.

Makes sense, which is why I was hopeful that the timer/switch would work.

The fault finding guide suggests:
"Ensure controls are set to demand and verify the contacts are closed."

But when I set to override/constant, there is no difference,
same with replacement timer.

Any idea what it means by verify the contacts are closed?

What would you suggest to resolve this?

adlplumbing · 27 Sep 2010

could have break in system what does not give the demand order
thus boiler does not fire up
anyware from clock to the pcb this includes the wiring

graemefarrer · 28 Sep 2010

Having replaced the clock with no joy
I think i will have to call in an engineer for this one.

My dad is an electrician but he is not familiar with boilers,
and said it would be more likely PCB damage than break in wire,
is he correct?

British Gas will be charging £168 to come out and fix this,
price is all inclusive, it this fair? or should I try a local engineer?

Any ideas?

kevplumb · 28 Sep 2010

link 1 & 2 on the terminal strip (opposite end to fuse)

petit_pablo · 28 Sep 2010

Yep ask your dad to try what kev said if your not happy to do it.

By linking out the extenal controls you will find whether the fault lies within or outside the boiler.

twgas · 28 Sep 2010

British Gas will be charging £168 to come out and fix this,
price is all inclusive, it this fair? or should I try a local engineer?

Of course it's fair, whether it's good value depends on the actual fault, they give you a quote and you accept it or not. The decision is yours. Remember if you go buying parts "thinking" that's the fault you'll have soon spent more than the £168 BG will charge you.

graemefarrer · 28 Sep 2010

I was really meaning to ask "was £168 a fair price to pay for british gas to come and fix my particular fault", if indeed they choose to fix it or not, as the service is no fix no fee, and if posed too time consuming or pricey for parts for them, they could simply decline to fix

in the end i contacted a boiler engineer, recommended from a friend at work, who has had a look at clock and diverter and has happened to get a wee electric shock off the casing. he thinks it needs a new wiring loom and possible replacement diverter

this could get pricey, as he suggests that if the parts cost £200-300 then i would be better off just getting a new boiler

should i get a second opinion before i actually pay for any work?

kevplumb · 28 Sep 2010

kevplumb said:
link 1 & 2 on the terminal strip (opposite end to fuse)

did you try

Beerlover · 28 Sep 2010

Get a second opinion the wiring loom is low voltage, except for the over heat stat.

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Baxi Combi Instant 105e HE - Hot Water Ok but NO CH

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