Hope this might be useful to someone with this boiler. Problem during winter 2015/16 of heating working fine but domestic hot water intermittent. According to Valliant when the hot tap is opened press i and should read S10 every time. (verified after repair). If not Aqua Sensor could be sticking. 8.8.16 Changed Aqua sensor (194819) and activator motor on Diverter valve (140429) to be on the safe side and it cured the problem.( Note how operating lever rides in and out of the housing and clips over the rod that operates the valve proper) (small brass part that came with Aqua Sensor original Vaillant parts kit not used in UK) Further unrelated problem with Pressure dropping December 2016 – Boiler pressure dropping and would not hold when more water admitted. Tested schrader valve at top of Expansion Vessel at the rear of the boiler– no water emitted indicating that interior rubber diaphragm was ok and not passing water into the air chamber. Changed Schrader valve(which looked absolutely worn out) and that cured the problem. In releasing pressure from the system using the Pressure Release Valve it would not reseal owing to the interior rubber washer having deteriorated. New PRV fitted and boiler working fine and pressure holding. NB: if the Expansion Vessel does need replacing it may not come out depending upon the flue configuration without a lot of work and the solution is to fit an external Expansion Vessel which is a fairly simple job costing far less in parts than the original Vaillant Expansion Vessel. (Vaillant themselves suggest this as a means of rectifying the problem)
Yes, the PRV is always an issue in almost every boiler - once 'triggered', they rarely close off again perfectly, and continue to be a pita. Sometimes it's a bit of grit from the system water that's caught on the rubber seal, other times it's chust that the rubber seal has conformed so perfectly to its closed shape that once it moves it doesn't sit in exactly the same position again.
Agree. In this case the rubber seal was in a very poor condition and one move was enough to disrupt it's ability to seal the valve. Seems a shame Vaillant don't market a replacement rubber seal rather than to replace the whole thing.
Had a call the other night from my cousin saying that he had a bad leak from his ecomax boiler. Found an 'o' ring from one of the joints to heat exchanger had perished. Fortunately had a box of assorted o rings and job done quite quickly. I'm certainly no heating engineer but was nice to be able to get it fixed there and then...for once!
Well done. Was this the Domestic Hot Water heat exchanger? Always keep a box of assorted O rings too. So useful for all sorts of things.
Yes it was, so fortunately accessible as its at the bottom of the case. Wouldn't touch the main heat exchanger...not safe for me to do so!
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