The Lochinvar blower is a variable-speed combustion fan that pulls air through the venturi and pushes combustion gas through the heat exchanger and out the vent. Failure triggers E09 fault.
How it works
- 120V variable-speed PSC or ECM motor depending on platform
- Hall sensor reports RPM to control board
- Control modulates RPM to match fire rate (10:1 turndown on Lochinvar mod-cons)
- Capacitor (PSC platforms) for start torque
Symptoms of failure
- E09 fault on call for heat or DHW
- Whining, grinding, or thumping bearing noise
- Inconsistent ignition (insufficient airflow during trial)
- Combustion analyzer shows abnormal CO2/O2 — wrong airflow
Diagnostic before replacement
- Capacitor test (PSC platforms) — bulging or out-of-spec capacitor mimics motor failure. $15-25 capacitor is the cheap first try
- Voltage at terminals during start sequence — control commanding motor?
- Free rotation with power off — seized bearings = replace
- Vent obstruction — blocked vent prevents motor from reaching target RPM and triggers E09
Replacement procedure
- Power off at breaker; gas off
- Open cabinet, disconnect blower power and tach signal
- Remove venturi and gas tube (some platforms)
- Unscrew blower from manifold
- Install new blower with new gasket
- Reconnect electrical and gas tube
- Verify combustion with analyzer (CO2 and CO targets per service manual)
Critical step: combustion analysis after replacement
Replacing the blower changes airflow characteristics slightly. Always perform combustion analysis after replacement to verify the gas valve trim is still correct. Adjust trim if needed (this is contractor work — proper tools required).
Cost
- Blower motor (OEM): $250-450
- Capacitor (cheap diagnostic step): $15-25
- Contractor labor: $200-400
- Total contractor service: $450-850
Lifespan
Combustion blowers typically last 8-12 years on residential combis with annual service. Skipping service shortens lifespan — debris in the venturi loads the motor.
Bottom line
Blower failure is a real possibility on 8+ year-old Lochinvar combis. Capacitor first (cheap test), then motor. Combustion analysis after every blower replacement.