Chamberlain H Owner's Manual page 18

Diagnostic Mode
Set dip switch to diagnostic mode. The following diagnostic codes are applicable:
G Obstruction sensed = 2 flashes then pause
G Board Okay = Rapid Flash
Factory Memory Preset
Activate this mode to initialize the board's memory to the standard factory preset
values. Set dip switch to diagnostic mode. Hold learn button down for 5
seconds. Diagnostic LED will go on then turn off when memory is clear. Sets
values to the following:
Maximum run timer = 90 seconds
Timer to close = 0 seconds
Mid stop = Disabled
Maintenance Alert System = Disabled
RPM Learn
NOTE: The RPM Learn should never have to be reset except in the case where
the Motor or Logic Control board has been replaced and only if the motor doesn't
have a start switch.
Set unit to any normal mode, B2 is suggested. Begin with the door in the open
or closed position. Set the limit switches so the operator can run for at least 5
seconds continuously at a steady speed.
Press the open or close button to start the operator. While the operator is
running, press the learn button on the board. The diagnostic LED will come on.
Hold down the learn button continuously while the operator is running. When the
diagnostic LED goes out, the steady-state RPM speed of the operator has been
"learned" by the microprocessor. If the unit hits a limit switch, or the motor stops,
or you release the button before the LED goes out (about 5 seconds), the RPM
learn procedure will have to be repeated. (Refer to figure 1 for RPM Learn
button location)
FIGURE 1
DIAGNOSTIC MODE & RPM LEARN
18
ON
ON
DIAGNOSTIC
1 2 3
OFF
4