Watchguard Firebox V200 Hardware Manual page 23

The fan status light changes to red when any one or more of the five fans
on the fan card are not operating. To maintain optimal cooling, the fan
card should be replaced promptly when the light is red. However, do not
remove the fan card until a replacement fan card is available. Removing a
fan card without having a replacement available will reduce cooling
capacity and may damage the boards or system.
When the replacement fan card is available, the fan card with the
inoperative fan can be replaced while the appliance is in operation.
Fan cards are not interchangeable because the fans on the first card are not
in the same positions as those on the second card. Fan cards are labeled
Fan1 and Fan2. Fan1 is in the left slot and Fan2 is in the right slot, as
shown in the front of the appliance illustration on page 10.
A fan card appears as follows:
Hardware Guide
C C
AUTION AUTION
Replacing a fan card
13