Error code reference

Lennox Furnace Error Code LED Flashing 1/2 sec on 1/2 sec off

Lockout or Restricted Lockout condition on the R7184B burner control.

First step from the service manual

Check limit switch contacts are closed and clean; check for line voltage at oil primary control (should be 120V); check if cad cell is exposed to external light.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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Step-by-step tests with expected resistance, voltage, and continuity values
Wiring diagram references and connector pinouts from the OEM service manual
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LED Flashing 1/2 sec on 1/2 sec off on my Lennox Furnace

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Lockout or Restricted Lockout condition on the

From Service Manual 747945, p.37:

1.Check limit switch contacts are closed and clean; check for line voltage at oil primary control (should be 120V); check if cad cell is exposed to external light.

2.Measure door lock assembly resistance across the PTC terminals. Expected: ~200 ohms cold, rising sharply once energized.

3.Inspect strike and latch alignment. A warped door or misaligned strike prevents the switch stack from closing in the correct sequence.

Part W10810403

Door lock assembly

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First step from the service manual

Get the full diagnostic procedure for LED Flashing 1/2 sec on 1/2 sec off.

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