GE JVM3150 Owner's Manual page 28

About other features.
28
Vent
When the microwave oven is off, you may
operate the vent fan:
1. Press the Vent pad once for high fan
speed.
2. Press the Vent pad a second time for
low fan speed.
3. Press the Vent pad a third time to turn
the fan off.
When the microwave is on, the vent fan will
automatically turn on at low fan speed, stay
on while the microwave is operating and
automatically turn off after the microwave
goes off if the Vent pad is not pressed.
When the microwave oven is on you may
also:
1. Press the Vent pad once for high fan
speed.
2. Press the Vent pad a second time for
low fan speed.
3. Press the Vent pad a third time to set
the fan to turn off automatically after
the microwave goes off.
If the vent fan is still operating after the
microwave goes off, press the Vent pad until
it turns off.
NOTE: The vent fan cannot be turned off
while the microwave is operating.