Just spent 3 cold days waiting for the replacements to arrive (boiler CH dial broke in off mode) and followed carefully your guidelines. Out of warranty and there was no way I was going to spend out on a clear case of it being a manufacturing fault, on what seems to be ATM a great boiler. Had I not been able to mend it, I would have insisted that Vaillant fix it (4 year old boiler) .... I mean after spending out thousands to fit an all singing and dancing bit of hi tec kit only for the control knob to fall off! The 'wonderfully complicated ' VRT 360f room temp thermostat has an open battery compartment that allows any leakage from batteries to leak onto thermostat motherboard. For some reason, this then caused (several times) new batteries to drain dead after only two weeks. With the Batteries dead ...the boiler for some reason would turn the CH on, and with no thermostat to turn it off, continuous heating operated. Dangerous or what? The plastic box slides out & down, stops at an angle, do not press it all the way down, leave it be

However as I rotated it to fit into it's slot shape (has a slit on a side, need to align correctly) IT FITTED INUnclip the 4 Plastic clips on the white box: 2 on top, 2 on the sides, use your flat screwdriver again gently I had a new Vaillant ecoTEC plus 937 installed in the autumn. All been well, boiler runs fine etc. Heating/water running ok (still). I know this is an old thread (well, nearly 4 months, but seems to be the exact same problem I have just found, so didn't duplicate).

Now you can see the innards , you will see that where the knobs go in is really a plastic box. And this plastic box can be released from teh frame easily, no screws or anything. Then you can open the plastic box open, if you wiggle with it you will probably already hear that there is something loose inside : it's the stems of the broken off knob(s) ! Look at the box, I believe there are 4 plastic lips that you need to loosen (just tilt them over the knobs that hold them in place). Once inside you will see the socalled motherboard, or PCB. And you will see that are two round places that oppose the place where the knobs would be inserted. You can also use a long piece of small square wood, shaved to fit at end, if your stem is too short (unlikely, they all break at the same place as mine) Product Information: The control knob resides on one of the spindles located on the front of the appliance and allows you to manually control certain aspects of the boilers functionality. Some boilers enable you to change temperature and some even allow you to change the current function. This means the user can have the boiler provide central heating without the hot water being on and vice versa. Boiler located in the garage and I went in there tonight to adjust the hot water temp on the boiler's control panel and the display did not adjust this time when I turned the knob at all. In fact the knob was loose and just came out of its recessThe knob broke on me, ecotec 824. It is easy to fix, even if you are not handy or elderly or a lady who does not do DIY, most ecotec models conform to below instructions: I switched off the heating at the programme panel (in the kitchen) as not needed heating on recently (last 2-3 months). The VAILLANT 0020074963 KNOBS, CPL. GREY (PK3) is a genuine, brand new Vaillant Boiler Spares product, covered by a Vaillant Boiler Spares manufacturer's guarantee. What needs to be done : first take the front cover off, there is only ONE screw that you need to loosen for this : it is underneath the CV heater, right at the front. Once that is loose you can take the whole front metal sheet off. Wrap lots of tape at the few milimetres on top of broken stem: TO FORM A KNOB to control temperature

So are any of you capable of posting a picture of what the knob looks like when it is not broken ? I assume that my knobs are broken but I do not really see where it broke off from... Very strange. The VAILLANT 0020048969 KNOBS GREY (PK3) is a genuine, brand new Vaillant Boiler Spares product, covered by a Vaillant Boiler Spares manufacturer's guarantee. Product Information: The control knob sits on one of the spindles located on the front of the appliance and allows you to manually control certain aspects of the appliances functionality. Some boilers allow you to change temperature and some even enable you to change the current function. This means the user can have the boiler generate hot water without the central heating being on and vice versa. We are proud of the quality of our refurbished parts and they come with 12 months replacement warranty. Your receipt will be the proof of warranty and please keep them somewhere safe. I bought one that did not have inner central rings like my broken one, I bought it yesterday morningI was wondering if now the boiler has been 'cool' for a long period, if the knobs were a bit snug and that contraction in some way has strained them?