Ariston Microgenus 31 - Diverter Valve Repair

Hi all, I was hoping for some tips from those who have done this before. Can I also say that I'm only up for DIY on the water side of the system. I don't think any of this will involve the gas side but if it does then rest assured I'll be on the phone for a pro.

My boiler died yesterday - dead as a dodo. It's a Microgenus II 31 MFI (NON HE).

I've identified that the gland seal has failed in the diverter valve allowing water ingress into the actuator motor which has blown the two fuses on the circuit board.

I guess I could have just dried the motor and replaced the fuses but I'd rather sort it properly.

I first isolated and drained the boiler. Then (after much difficulty and swearing) managed to chip out the remains of the snapped-off retaining clip lugs which had rusted into the valve body. This allowed me to remove the actuator motor which as predicted was very wet inside.

I then removed the secondary heat exchanger cover and then the secondary heat exchanger itself. As a side note, this has a label showing which direction is UP however it appears to have been fitted in the opposite direction. Not sure if that is important?

Finally, I prised off the clip on the pressure relief pipe at the rear and undid the other nuts, wires and base screw and got the valve itself out.

I removed the spring/pin part from the top and have ordered a replacement (in the form of a diverter valve repair kit) from that auction site which is arriving tomorrow along with a replacement (presumably 3rd party) actuator motor.

I need to track down somewhere local to the midlands who sell the two fuses which are 20mm x 5mm F2AL250V. I also need to track down 4 new o-rings to fit to the secondary heat exchanger as the others look worn and are virtually flush with valve body. I can't see how the others look on the drain valve side. Do these generally need changing too? I also want to track down the appropriate size fibre washers for the various connectors.

It's easy enough to find part numbers from the Ariston manual but they don't state sizes. My local CityPlumbing seem to have O-Ring (part number 573825) for £5.15 - hopefully that is for a pack of 4 as they only have 1 in stock.

If I can't find anything locally then Amazon have a mixed pack of quick blow fuses although I can't see if they have the L designation. I could also get a mixed pack of O-rings but I'm not sure if they need to be a certain type to resist the heat?

There does seem to be a bit of corrosion on the inlet/outlet ports of the secondary heat exchanger to the inner edge of where the o-rings sit. I think it should be OK - not sure whether they usually fit back OK after 15 years untouched?

Also wondering how best to clean up the surfaces before using the new fibre washers. Is it OK to use the old ones? Maybe clean up the mating surface with wire-wool?

I'd be grateful for any hints and tips that will help me to get this fixed up correctly first time.

Thanks!

you have given yourself an awful lot of work that you didnt need to do, you simply remove the actuator motor, undo the cartridge retaining nut, fit replacement and attach new actuator , re fill and job done, 20 mins maximum, the fuses are readily available , any electronics shop will have them, there was no need to remove anything else, there are sometimes spare fuses on the inside of the white control cover

Thanks Ian, you are quite right. I realised at 2am last night as I unscrewed the cartridge nut that I needn't even have spent 2 hours picking out the remains of the rusty retaining clip, I could just have unscrewed the cartridge and motor in one go! You live and learn I suppose.

Given where I am, and having removed the o-rings from the back of the diverter valve and there is quite a bit of crud in the recess although the o-rings have cleaned up fairly well. What is a good method of cleaning out the recess? Is wire wool OK or will the bits get into the valve?

Get_Army said:

Thanks Ian, you are quite right. I realised at 2am last night as I unscrewed the cartridge nut that I needn't even have spent 2 hours picking out the remains of the rusty retaining clip, I could just have unscrewed the cartridge and motor in one go! You live and learn I suppose.

Given where I am, and having removed the o-rings from the back of the diverter valve and there is quite a bit of crud in the recess although the o-rings have cleaned up fairly well. What is a good method of cleaning out the recess? Is wire wool OK or will the bits get into the valve?

Click to expand...

as you have it all stripped out now, I would just scrape the recess with a srewdriver or the like , and wipe clean with paper towel or something and a smear of silicon grease on the O rings should see you fine