Vaillant boiler repair

[Karel]

I just repaired my Vaillant boiler. I post the solution here so that it can be of use to others.
This boiler has a pcb that is used in many boilers of many different brands, so this could be applicable to
other brands/models as well.

Brand: Vaillant

Model: turboMAG 11-2/0

PCB: SYMSI7.0   label (S/N??): 0020053292 10027 2354

Symptoms/problem description:

Initially the boiler works ok. When opening the tap for hot water, the boiler funtions normally and hot water arrives.
When closing the tap, the boiler stops heating the water but the internal fan keeps on running. The display is NOT indicating an error!
When opening the tap again, water arrives but it's not heating and the fan keeps running. The display is NOT indicating an error!
Closing the tap, waiting a while, and opening again doesn't help. The fan keeps on running and the boiler will refuse to heat the water.  The display is NOT indicating an error!

The only work around is: switch-off the power of the boiler, wait for a couple of minutes, switch-on the power again.
Now it works again, that is, untill after you tapped hot water, then the story repeats.

Long story short, the circuit that is responsible to switch-on/off the fan was not working correctly.
The cullprit was either an optocoupler/triac driver or the triac. These components are so cheap that I didn't bother and replaced them both
(without checking which component was defect).

Here are the components I replaced:

MOC3023M (optocoupler/triac driver) indicated on the pcb with designator ISO100E

BTA208-600B (triac, I replaced it with a BTA208-800B)

The pcb is pretty expensive, so, if one can repair it, the better. Good luck!

[tggzzz]

In many countries there are strict regulations about who can open/service/repair gas appliances.

That's good, since there are too many examples of "Dunning Kruger" repairs causing houses to rapidly disassemble themselves.

[perieanuo]

In many countries there are strict regulations about who can open/service/repair gas appliances.

That's good, since there are too many examples of "Dunning Kruger" repairs causing houses to rapidly disassemble themselves.

on the other side, in my country the repair techs are low cost cheap mfkers with almost 0 electronics deep knowledge at their tech level, so NO ONE repairs those pcb's
that's why i repaired that type of hw for my neighbours and 'connaissances' because it's not normal to throw out the control unit for a simple defective relay or small signal triac for example.
it's enough we are pushed to always consume and consume more, repairing what's reasonable repairable should be imposed by state norms, changing some opto/triac is the AB of electronic repair.
so congrats for op, good job, keep on
zero risk replacing some component like this with equivalents if done by the rules

[pcwrangler]

I say good for the OP. Nearly everything on this forum has the ability to burn down their structures but here we all are. Be smart. Be safe. Be free.

[Karel]

No offence but my experience is that "professionals" don't bother with replacing components on a pcb.
They simply substitute the pcb and charge you for it.
I get it.  Like all electronics today, fault finding and ordering and replacing defective components requires time,
a lab and an experienced technician. So, it's usually cheaper to replace the pcb...

[Jwillis]

No offence but my experience is that "professionals" don't bother with replacing components on a pcb.
They simply substitute the pcb and charge you for it.
I get it.  Like all electronics today, fault finding and ordering and replacing defective components requires time,
a lab and an experienced technician. So, it's usually cheaper to replace the pcb...

This is why everyone needs to get on board with the Right To Repair movement, Companies want to keep secrets about the products they produce so when it fails, people have no choice but to increase the size of land fills. People need to start demanding that any products they purchase can be repaired by independent service people. And that all information concerning the repair of such products be made openly available Or at the very least when a product becomes replaced by a newer version. The current methodology of a Throw Away system is not sustainable economically nor environmentally. The whole social economic system needs to change. 

[Karel]

The whole social economic system needs to change.

It would be a big step to make it obligatory to provide free service manuals including schematics, partslist and adjustment
procedures (all in pdf), the same as with owners manuals.

[Chris56000]

Hi!

It would be a big step to make it obligatory to provide free service manuals including schematics, partslist and adjustment
procedures (all in pdf), the same as with owners manuals.

. . .And any special adjustment or calibration/setting up software as well!

Chris Williams

[Swake]

Where are the times that devices came with the schematic in the box. I remember that many TV's and some radio's had them attached in an envelope inside the device. Somewhere in the 80'ies of last century this practice stopped.