Combi boiler diaphragm help

[Tekquest]

I've got a Vokera Maxin 24e.

The radiators are working fine, however the hot water runs cold (tepid if the rad's are on).
I've replaced one of the micro-switches as it seemed a bit discoloured around the contacts.

I've tested each micro switch, and the boiler fires up when I manually engage each switch.

After some messing around, I've managed to narrow the problem down to a faulty diaphragm (I think). If I remove the switch mechanism from the pin/plunger, pull out the pin to around the same distance in which it would engage the switch, and at the same time press the button on the switch to make contact, the water run very hot, however when I let go of the pin, it recedes back into it's housing and the water runs cold again.

I'm thinking that the diaphragm is faulty, if so, it's around a fiver to buy a new one.

How much should I expect to pay to have this replaced, how long would it take, and is it something that could be swapped out by a competent DIY'er?

Prices quoted so far are between the £70 - £80 mark.

 

[Pete_London]

£70 - £80 mark sounds a fair price tbh.

 

[ekwat]

It is a DIY job as I've done it on a Vaillant unit but £80 seems suspiciously reasonable to me.

 

[rawsy]

My old fellas boiler had issues with the thermo coupler and diaphragm . We were lucky cost me about £ 15 plus a pint for a mate to sort it for me.

 

[hatab]

i have a baxi combi and have replace the diaphragm (split) when had the same problem it didnt take long to fit.

If you have got this far in your diagnosis you are obviously competent enough to find your way around.

i wouldn't play around with the gas side but it just mechanical/pressure switch what you are doing for a fiver its worth a go.

 

[Tekquest]

Thank's for your replies guys.

I'll pick up a replacement diaphragm from Plumb Centre tomorrow, if I think that there's any risk at all from flooding the place, or it going wrong, I'll call a man that can. If nothing else, at least I won't get stung with the cost of the part.

 

[DW190]

Perhaps the PDF attached will help.

 

[Tekquest]

Thanks for the installation manual DW190, I managed to grab this from the Vokera site last night, and with the instructions below (from another site), I'm all set to replace it when I get the part

To remove the diaphragm, turn off cold water to boiler and open lowest tap in house. There are two differential tubes going into the top of the valve where the diaphragm is. Remove both clips holding these tubes in and remove, they are sealed with orings. There is a grub screw or two holding the valve in place. Unwind these a bit and the brass valve will come out. Now undo the 6 screws, note which way the diaphragm is sat and replace with new. Put back together in reverse, replace the two orings if you can.

I am more than competent (and also confident) in carrying out this job, the worst that can happen is I get wet and incur a hefty repair bill. There's no way I would attempt anything on the gas side of things though.

I love the internet :THANKS:

 

[gasman]

Fairly simple swap on these but make sure to replace any o rings or at least grease them with something suitable you shouldn't get wet but as a precaution ensure the cover that holds the pcb board is protected.

 

[Exos]

This is one of the reasons why I pay British Gas £12 a month.

My last issue the part alone was £85 ex vat. and I had them out three times for different things.....

 

[Tekquest]

Well that was interesting.

It took no more than 30 minutes from start to finish, and that was me taking my time. I was going to replace the o-rings as well, but Plumb Centre didn't have any in stock, I'll fit new rings at some point though, no great rush.

The only bit of me that got wet was my fingertips when I dismantled the diaphragm housing to remove the old one, there were no splits in the rubber, but it was perished and misshapen. I replaced everything, turned the water back on at the main, and once the water had went through the system, fired up the hot water. It was scalding hot, result.

Everything was fine until about an hour ago. Everything made the right noises when the hot water and heating was switched on, but the gas didn't light. I waited a while, then tried again, it fired up as normal.

I've increased the mains pressure a bit, it did the same with everything seemingly working OK, but not firing. After a while it worked again.

It did the same again, so I pulled the fuse for a few minutes, put it back in and left it for about 10 minutes, and again it was OK.

I'll keep an eye on it for now, and will do some more digging to see if there's anything that could be causing it. Maybe it's natures way of telling me to get cover?

 

[DW190]

This is one of the reasons why I pay British Gas £12 a month.

My last issue the part alone was £85 ex vat. and I had them out three times for different things.....

I fit a Gloworm boiler and 8 rads myself 30 years ago. Serviced it my self (cleaned the burner and checked for leaks) and over the 30 years replaced the boiler thermostat and a thermo coupling and replaced the pump. Probably cost about 70 quid altogether..

I only replaced the boiler because I lost my gable end (son had house built and attached to ours) where the balance flue was and couldn't get a vertical conversion.

£12.00 per month for thirty years for me would have been £3,600.

 

[Pete_London]

"This is one of the reasons why I pay British Gas £12 a month.

My last issue the part alone was £85 ex vat. and I had them out three times for different things....."


Better off keeping the money in the bank, then just get a competent engineer in when the time comes.