TM 9-2320-273-20
Section XVIII BLACKOUT LIGHTING SYSTEM
2-50. INTRODUCTION.
The blackout lighting system prevents operation of the horn, backup alarm, and all service lighting
(para 2-43), except instrument lamps, and dome lamp. The system provides the following intensity
lighting for blackout operation on all M915 series vehicles:
a.
One headlamp.
b.
Two front marker lamps.
c.
Two tail and stop lamps.
d.
Trailer tail, stop, and marker lamps on M915, M916, M917, and M920 at the 12-pin
trailer receptacles.
2-51. BLACKOUT LIGHTING SYSTEM.
NOTE
In reading the following component de-
scription you should remember that the
OPERATION switch is in BLACKOUT
position.
1. BLACKOUT HEADLAMP. The lamp consists of a single, replaceable sealed beam unit. With
the headlamp switch in the ON position, the blackout headlamp is energized by a 12-volt
battery power.
2. BLACKOUT MARKER LAMPS. Each lamp consists of a replaceable bulb which is energized
by 12-volt battery power when the headlamp switch is in either ON position.
3. ClRCUIT BREAKER (CB-8). Protects electrical components for 24-volt blackout stop lamp
relay circuit by opening when load exceeds 20 amps. Automatically recycles until overload
is removed.
4. RELAY (K5). Normanlly open contacts: Closed by 12-volt power when the operation switch
is in BLACKOUT. When relay is energized, 24-volt power is supplied from circuit breaker
CB-7 through 24-volt trailer receptacle for blackout tail lamps.
5. ClRCUIT BREAKER (C B-7). Protects electrical components for 24-volt blackout tail lamp
relay circuit by opening when load exceeds 20 amps. Automatically recycles until overload
is removed.
6. RELAY (K4). Normanlly open contacts: Closed by 12-volt power when the operation switch
is in BLACKOUT. When relay is energized, 24-volt power is supplied from circuit breaker
CB-8 through 24-volt trailer receptacle.
7. ClRCUIT BREAKER (CB-1). Protects electrical components for stop switch circuit by open-
ing when load exceeds 20 amps. Automatically recycles until overload is removed.
8. 24-VOLT TRAILER RECEPTACLE (M915, M916, M917, and M920). Tractor mounted 12-
pin connector to provide 24-volt battery power to Iunette - towed trailers for blackout tail
and stop lamps. This receptacle is 12-volts on M917.
2-58
