Medium
C2 on Viessmann Vitodens 343-F WS4A

Your boiler has lost contact with the solar panel controller, so it can't use the sun to help heat your water, but your heating and hot water should still work normally.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Control mode - Communication fault, solar control unit

From this model's manual
Verified against the Viessmann/Viessmann Vitodens 343 F Ws4a 5592883 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like C2: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

C1View →C3View →

All 59 fault codes on the Vitodens 343-F WS4A

Seeing a different code? Every code this model can display, in one place.

0F9A9b9C9F10182028303840485058929394A6A7b0b1b4b5b7b8bAbCbdbEbFCdCECFdAdbdddEE4E5E8E9EAEbECEdF0F1F2F3F4F8F9FAFCFdFEFF

Related guides you might find useful

No hot water but heating works

Almost always a stuck diverter valve on a combi.

Read →

Banging, kettling or whistling noise

Each noise points to a different fault.

Read →

Boiler won't turn on: 9-step checklist

Work through these before the call-out.

Read →