OIL PRIMARY CONTROL LED DIAGNOSTIC
The LED diagnostic light has several functions. It
indicates the state or mode in which the oil burner is
operating. It will also indicate fault conditions, and help
determine cad cell resistance while the burner is
The LED diagnostic light will turn on when the burner
enters the carryover state; the point at which ignition
spark is on, and will remain on through the run state,
where the ignition spark is terminated but the burner
continues to fire.
The LED diagnostic light will turn off at the end of the
burner cycle as the oil primary control enters the idle
state, and will remain off until the next heating cycle.
If the LED diagnostic light is flashing quickly; 1 Hz (½
second on / ½ second off), the oil primary control is in
the lockout state or in restricted mode. To exit the
lockout state, press the reset button.
If the LED diagnostic light is flashing slowly; ¼ Hz (2
seconds on / 2 seconds off), the oil primary control is
in the recycle state. This indicates that flame sensing
was lost after the lockout timer expired during the
ignition carryover state. The oil primary control will
return to the idle state within 60 seconds.
CAD CELL CONDITION:
If the LED diagnostic light is off, the cad cell is not
If the LED diagnostic light is on, the cad cell is sensing
flame, or viewing ambient light.
The resistance of the cad cell may be checked while
the oil primary control is in the run state by pressing
the reset button. The LED diagnostic light will flash the
Table C-2: Cad Cell Resistance
Resistance in Ohms
Less than 400
Between 400 - 800
Between 800 – 1600
Between 1600- 5000
IMPORTANT: Due to the potential hazard of line
voltage, only a trained, experienced service technician
should perform the troubleshooting procedure.
Check the diagnostic light for indications of burner
condition. Refer to the oil primary control LED
section for details.
WHEN SIMULATING A CALL FOR HEAT AT
THE OIL PRIMARY CONTROL, DISCONNECT
AT LEAST ONE THERMOSTAT LEAD WIRE
FROM THE T1 - T2 TERMINALS TO PREVENT
DAMAGE TO THE THERMOSTAT.
NEGLECTING THIS PROCEDURE MAY BURN
OUT THE HEAT ANTICIPATOR OF A
STANDARD 24 VAC THERMOSTAT, OR
CAUSE HARM TO COMPONENTS WITHIN A
Before checking the oil primary control, perform these
preliminary checks, (repair or replace controls as
Check the power supply; fuse box or breaker,
any service switches, all wiring connections, and
burner motor reset button (if equipped).
Check the limit switches to ensure that the
switch contacts are closed.
Check the electrode gap and position.
Check the contacts between the oil primary
control and the electrodes.
Check oil supply (tank gauge).
Check the oil nozzle, oil filter, and oil valves.
Check the piping or tubing to the oil tank.
Check the oil pump pressure.
CHECK OIL PRIMARY CONTROL AND
If the trouble does not appear to be in the burner or
ignition hardware, check the oil primary control and the
igniter by using the following equipment:
Voltmeter (0 - 150 V
Insulated jumper wires with both ends stripped.