Hello everyone, I'm looking for help with a recurring Optolink communication failure between my Vitoconnect and the boiler. Device details Boiler: Viessmann Vitodens 222-F B2TA, 19 kW (sold 2016), serial 75130446…8101 Communication module: Vitoconnect 100 OPTO1, serial 75713818…9106 Symptoms Wi-Fi is stable, signal -41 dBm ("excellent" in the app). The boiler communication LED flashes red, and the ViCare app shows a boiler communication error (screenshots and LED photo attached). The boiler display shows no fault codes at any time. The problem seems limited to the Optolink communication. What I have tried Replaced the Optolink cable with a brand-new Viessmann one (Art. 7856059). The behaviour is identical, so it is not the cable or reader head. Cleaned the Optolink port on the boiler casing with isopropyl alcohol and power-cycled the system. Key observation: right after cleaning or a power restart, communication works (LED turns solid green, ViCare shows data). After only 2-3 minutes it drops again and the LED returns to flashing red. This suggests the optical path is partly functional but degrades quickly in operation (possibly thermal drift, an unstable optical transceiver, or a UART fault on the control PCB). Questions Is the Optolink diode/receiver assembly available as a separate spare part, or does this point to replacing the main control PCB? Are there any diagnostic tests or firmware/parameter checks I should do before ordering parts? If a hardware swap is needed, what are the correct part numbers for my serial number? Thank you for any advice!
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