I've got Vaillant CalorMatic 240 in my apartment. During the coldest day so far, this piece of work decided to die on me showing only "batt" message.
After some Googling around, I've discovered that it's a signal for dead batteries. Oh but wait, there's exactly 3 models like yours and absolutely NO manuals on disassembly. Gorgeous!
That's why I've decided to write this short blog on disassembly of this piece of work !
The first thing I did was of course, prep up the iFixit toolkit and started to dig!
The plastic was really hard to take down, it was flexing so hard I've thought it's going to break apart.
Only smart move was to pry each piece a bit and use flash to check where the clutches are.
Turns out there's only 2 clutches at the bottom part, which are really really tight. The case plastic has been bent while I've pushed it out, so take care of that!
aand boom, got you now!
First thing noticeable is the sticker with the model number on it. This is the first sign of a model I've seen so far.
Apparently it's powered by triple A batteries. There are 4 pins, which I've assumed 2 are data and 2 are power lines.
After some testing with the batteries, turns out all 4 of them are comm pinouts. Couldn't find any more details on them online.
Front side is also quite interesting. They've used rubber contacts for buttons, which is quite good considering how much they've ruined that slider on the right side.
After searching around, I've managed to find no information on that chip, except the few Chinese distributors selling it.
Nothing too interesting there, time to replace the battery and push it back into the wall!
After returning it into plastic case, it wouldn't work for some reason ?
With direct contact, it seems to work flawlessly and the temperature reading is correct!
Time to fit it back into the plastic, somehow..
The plastic mounts are really soft, I've bent them easily so I could fit the motherboard into the mounts.
After it's been fixed in plastic mount, it just needs to be pushed back into the wall. No extra effort needed!
It's interesting that after I've returned it, the temperature readings gained a -2 Celsius offset on readings again.
Geniuses at Vaillant probably didn't think it's going to get wrong readings from being mounted on the cold walls...
Thanks for reading!