E-340: Combustion air fan fault

Q: How do I check a E-340 fault?

1. Check fan motor and overload 2. Inspect damper linkage 3. Test air proving switch Safety: Boiler work must follow site permit-to-work; never bypass safety controls.

Probable causes

Fan motor overload
Damper linkage fault
Air proving switch fault

Step-by-step checks

Check fan motor and overload
Inspect damper linkage
Test air proving switch

Safety: Boiler work must follow site permit-to-work; never bypass safety controls.

Sample code — verify with the OEM manual for your exact model.

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Frequently asked questions

What does E-340 mean on a Steam Boiler?

E-340 usually indicates: Combustion air fan fault. Confirm the meaning in the manufacturer's manual for your model.

What causes E-340?

Fan motor overload; Damper linkage fault; Air proving switch fault.

How do I check a E-340 fault?

Work through the numbered checks above in order, recording readings as you go. Boiler work must follow site permit-to-work; never bypass safety controls.

Other Steam Boiler codes

Disclaimer: Fault code information is guidance only. Codes and meanings vary between manufacturers and models — always follow the manufacturer's manual and your site's safety procedures, and use qualified personnel for electrical, pressure, refrigerant and combustion work.