Vaillant heating problem

[DJ46]

the boiler switches itself off and displays the flashing radiator sign. If I change the d2 setting to 2 mins then after the 2 mins boiler comes on but very quickly shoots up to the 70° (and then to 72°) and shuts it self down again, so the boiler is on at most for around 10seconds. If I change the d2 back to say 15 minutes then this appears to give it long enough for everything to cool down and it reverts back to beginning of this paragraph. The important thing is that never does it get warm enough for the room thermostat to switch it off, the boiler internal thermostat always cuts in first. It runs 15mm bore upstairs and I believe plastic pipes in wall and then a small amount of microbore connecting downstairs rads. Last year I removed all rads and flushed each one out and this year I have drained system and flushed out several times so it is certainly not clogged up. This seems to happen whatever temperature I put boiler at i.e 55° as opposed to 70°. I read somewhere that it could be the micro switch in the three port valve and my valve certainly seemed stiff and was getting very hot (hotter than the water flowing through it) so I have replaced this and it appears to have improved matters but problem still persists. Incidentally when I removed valve it was fairly clean in the pipes and certainly not seized. Pump spindle is free and appears to work well at all speeds. Any suggestions?

 

[DJ46]

I have just posted this but it appears to have missed off the front part so here goes again
I have a 2011 vaillant ecotecplus415 and normally shut it down for summer. I have just tried to re start it and it came on fine and after about 10 minutes boiler temp gauge got to where I had put it, in this case 70 degree. Boiler then worked for about half an hour and then gradually creeper up to 72degree and boiler shut down to protect itself, the radiator symbol then flashed but the temperature in house had not reached what I had set room thermostat at, in this case 20degree. After 20 minutes boiler came back on and did same thing. I changed the d2 setting from the 20 minutes to 2 to save time but after only 2 minutes boiler would come on but would rocket to the 70 degree and turn itself off. Boiler stays on for only 10 seconds at most.

 

[rpm]

Afraid I only have one suggestion as it is gas .............

[DLMURL="http://www.ukplumbersforums.co.uk/im-looking-plumber-gas-engineer/"]I'm looking for a Plumber or Gas Engineer[/DLMURL]

 

[Rickster123]

Good advice given.

This plumbing forum will not provide advice to anybody with regards to boiler repairs or any other form of gas plumbing without you first providing us with your Gas Safe Registration number in a thread - for very obvious reasons. If you're not qualified to touch gas, you should stay well clear of trying to!