Vailland 200 3-5 Boiler: Error F26 Persists Even After Motherboard Replacement

Hello to all forum users. I have a problem with the gas stove, after switching on, the code f26 is displayed and all functions are blocked. After the initial analysis, the service technician suggested replacing the motherboard. I installed a new board, the problem remained.

Error F.26 according to the instruction is:

Rather, it indicates a fault with the gas valve or wiring harness.
The motherboard could also be damaged, but why did the service technician start with the most expensive component?

bronek2103 wrote:

Hello all...

Buddy, this error is related to the gas valve and that's where you should look. Firstly, a stepper motor, secondly, the wiring of this apparatus (i.e. the entire harness, including the printed circuit and plugs on the motherboard), thirdly, the ntc sensors (this is additionally because there may be a wrong sensor indication and the signal for the gas apparatus and it "stands" and crashes error f.26).
In the end, I would insist on the motherboard.

And by the way - not Vailland but Vaillant, not just a boiler

The motherboard has a new one. When I turn on the boiler, you can hear as if an engine stabilizes something after a few seconds, the display shows f26 and everything is blocked. .

what you hear after turning it on is probably the characteristic buzzing of the motor from the three-way valve.
If the service technician started, let him finish.
I advise against "fumbling" at the gas valve on your own.

I made an appointment with a service technician today, we'll see what the final will be.

bronek2103 wrote:

When I turn on the boiler, you can hear something like a motor stabilizing something

Each time the boiler is turned on, the gas valve, CH - DHW switching valve and pump are activated to check their correct operation.

Hello. I installed a new gas valve today. The stove is running like new. Thanks everyone for the advice. I am closing the post.