This task cannot be performed without the special tools listed in the technical manual.
Ensure their availability and serviceable condition. These required items are:
Familiarity with the driver's night vision viewer AN/VVS-2(V)1 is necessary to
effectively perform this task. Figure 4-1 illustrates the primary controls and indicators of the
The TM 11-5855-249-23, Chapter 4, paragraph 4-10 (see TM extract on page 95) gives
the prescribed procedure for the purging and pressuring of the driver's night vision viewer
AN/VVS-2(V)1. This procedure requires the use of the purge kit, fire control with purging
wrench and adapter assembly. However, the purge device can also be employed to purge the
driver's night vision viewer. The following procedure is recommended: (See Figure 4-2.)
Ensure valves are closed on the fire control purging tool and nitrogen tank before
connecting equipment. Connect purge kit, fire control to nitrogen tank and purge
device as shown in Figure 4-2.
Set regulator valve handle (1) to zero by rotating control (counterclockwise) until
there is no spring pressure on control.
Open nitrogen tank valve (5). The high pressure gauge (4) will indicate tank
pressure. If pressure is below 50 pounds, replace tank.
Set purge device (8) PUMP/NITROGEN switch (11) to PUMP and LEAK
TEST/PURGE (10) switch to PURGE.
Slowly adjust regulator handle (1) by turning it clockwise until low pressure
gauge (3) indicates 3 + 1 PSI. Purge device gauge (9) should indicate 0 + 1 PSI
and you should hear gas escaping.
Use a number 1 Phillips screwdriver to ensure that gas outlet ports (sealing screw)
Gas outlet ports are located on side of viewer with operating controls.