boiler problem: got heat, no hot water, taps make it click

[choppachimp]

yes I know my Saunier Duval 623 combi boiler is well past its best before date and yes i know they are prone to leaking like a sieve once they reach a certain age... However @ 3.5K for British Gas to replace the unit, I'm going to have to make do again this winter!

For 6months it had leaked water and for the last 4months we have had heating (if we wanted) but no hot water.

It was leaking from the water diaphragm valve, (now called a Water Valve part #05239800). I know this as the extremely helpful SD helpline took a look at the pictures I sent them, so I could purchase the correct part (which I did).

I've just replaced the Water Valve (thanks Kev) but although I dont have a leak now, I still dont have hot water

When I open a hot tap the boiler clicks like its going to fire up, but never does the full rumble & flame thing it does, say when you put the heating on.

Even with the heating on and then opening a hot tap, I initially get hot water, but only for a short period and this seems to quash the ferocity of the flames through the pilot window.
The moment you turn the hot tap off the boiler clicks and fires up with its usual rumble and heating continues.

reading through the Fault Finding Flow Diagrams, the next thing it suggests is the sealing washers on the reversing valve. Now as this is a multi part breakdown, should I even attempt to try the next part it suggests?

What are YOUR thoughts on what might be going on in my boiler based on the description (and yes I know replacing the entire boiler would be an ideal solution! )

TIA

 

[Boilerman2]

BG's Quote of over £3.000??? OUTRAGEOUS!

Contact a reputible local RGI you should be able to get AT LEAST 50% saving on that BG Quote

Saunier Duval = flogging a dead horse

 

[mickyg]

I think your gonna struggle DIYing this one. When you open a tap, the pin from the water valve should activate 3 microswitches, labelled microswitch 1,2 and 3 in the boiler manual and wiring. If these activate the pump and fan should operate, if its not getting to that stage then the microswitches may not be operating. It sounds like you still have a problem with the water valve, but I can't see how it could be fitted incorrectly..
btw your BG quote is outrageous. Get some other quotes.

 

[choppachimp]

it does sound like micro switches clicking (funny enough) when I crack open the hot tap, it just doesn't seem to fire the gas or the big ignition, as it where.

As at test I've just left the heating running for a couple of hours and its all warm and toasty and not a drop of water under the boiler.

Yes the BG quote was outrageous, I wont bore myself with why...but I got it out of curiosity and cause they where adverting special winter deals yadda yadda...

May resort to a reputable boiler from Screw-fix and a local installer to keep it as cheap as poss. May give SD Helpline a ring again on Monday and see what they suggest (they where spot on with the leak issue)

 

[mickyg]

Do you know if the pump and fan are operating when you open the tap? as I suggested, it may not be activating all 3 microswitches. tbh though you should really consider replacing it asap. Their actually failry reliable up until the point something needs changing, then it leaks forever more!

 

[choppachimp]

cheers Mickey,

surely the pump and fan MUST work for the heating??? that fires, clicks and farts all as it should...

any way to manually trigger these by bypassing the micro switches? (that unit comes out pretty easy, as I had to remove it to get at the water valve)

 

[Agile]

Isn't this "helpful" S-D helpline a premium rate telephone number?

A straight forward boiler replacement should not be much more than about £1600 for the cheaper boilers or about £1900 for more expensive ones. All prices inclusive buit not including the TRVs which are recommended when fitting a new boiler.

I do have to say the S-Ds are some of the WORST boilers on our planet and once they start leaking i would say its time to replace it.

I once saw one abandoned in the B&Q car park. Looking very new I stopped and saw that it was only 2 1/2 years old! Someone was fed up with it after so little time !

Tony

 

[mickyg]

yes they work, but if the switches don't make, then they won't receive power! I can't remember which switches are what, there's quite a few on that boiler! It generally baffles even reasonable heating engineers let alone DIYers! I think you will struggle to fix this yourself but by all means have a go, as I suspect you'll struggle to find anyone to repair it for you!
I went to one last year that had a few faults, I managed to get it sorted in the end, but it was murder. You can re-assemble it as well as you like but it can still leak on joints.

Untitled

• mickyg
• 24 May 2009
• 5

 

[Gasguru]

Pull off the wiring connectors from the microswitches on top of the reversing valve. Using a multimeter set to continuity (or lowest ohms range) check the switches operate as the hot tap is opened/closed. Check resistance is an ohm or less.

Internal washers on the reversing valve paddle have nothing to do with your problem.

 

[choppachimp]

Mickey, all good advice, appreciate it

Gasguru, nice one, I'll have a look with my multi meter tomorrow

 

[choppachimp]

Pull off the wiring connectors from the microswitches on top of the reversing valve. Using a multimeter set to continuity (or lowest ohms range) check the switches operate as the hot tap is opened/closed. Check resistance is an ohm or less.

Internal washers on the reversing valve paddle have nothing to do with your problem.

so having done that, numbered left to right 3 2 1

three pin 3: top/mid pins: Tap on: continuity. Tap off: no continuity
three pin 3: mid/bott pins: Tap on: no continuity. Tap off: no continuity
three pin 3: top/bott pins: Tap on: no continuity. Tap off: continuity (note opposite of first reading)

two pin 2: Tap on: continuity. Tap off: no continuity

two pin 1: Tap on: continuity. Tap off: no continuity


all in all it would appear the switches are functioning IMO, but what they are connected to, well thats a different matter!

How does the actually tap on process get sensed by the boiler?

on opening the tap, water seems to pass through the Water diaphragm Valve I just replaced, does it trigger a pin that in turn closes the micro switches (depending which way the Heating/No Heating lever is positioned?) ...these circuits in turn fire up the gas jets, the fan and the pump, heating the water now passing through the boiler.....exiting the unit and flows out the hot water tap via the hot water pipe work.? <curious>

Could the pin/lever mechanism be my next port of call? or the fact the switches do something on opening the Tap, means the problem is on the other end of those 3 circuits?

 

[choppachimp]

having gone back to the Helpline with these findings it was suggested that the micro-switches where at fault:

On the replacement part, there are 3 terminals on every micro switch and there is an additional fixing screw. Also the left fixing screw is much longer, although the new part came with two longer screws supplied. I appreciate parts can be updated and also designed to fit more than one model, so I tried them in the boiler regardless.

This made no difference to the lack of hot water. Still a clicking can be heard when the hot water tap is opened but the boiler does not fire up and produce hot water.

Attempted to book a qualified Saunier Duval boiler engineer, but was refused on the grounds the model is obsolete.

What else can I test on the ends of these three micro switch circuits?

TIA