What does the Vaillant d.37 fault code mean?

Your boiler is struggling to control the intensity of its flame, which stops it from heating your water and radiators efficiently.

How much does it cost to fix Vaillant error code d.37?

Typical repair cost for the Vaillant d.37 fault is £180-£350 including labour.

Modulator current

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Older boilers — thermocouple, draught, gas supply.

Sludge build-up — needs flushing, not bleeding.

Safety-critical — turn off, read this.