TM 9-2320-273-20
2-45. MARKER AND CLEARANCE LAMPS.
When headlamp switch is in either ON position, the operation lamp switch is in NORMAL position,
12-volt power is supplied to illuminate clearance lamps and front marker lamps as well as the trailer
marker lamps on M915, M916, M917, and M920 vehicles. The trailer marker lamps receive power
through receptacles mounted on the tractor chassis.
1.
MARKER LAMP ASSEMBLY. Each assembly has two bulbs that illuminate whenever
headlamp switch is ON and operation lamp switch is in NORMAL. One bulb is used as a
marker lamp, and the other is for turn signals (para 2-46).
2.
RELAY (K6). Normally open contacts; 12-volt power energizes relay when operation
light switch is in NORMAL and headlamp switch is ON. When contacts of relay close, 24
volts from circuit breaker CB-8 is supplied to tractor chassis receptacles.
3.
ClRCUIT BREAKER (CB-8). Protects electrical components for 24-volt tractor receptacle
circuits by opening when load exceeds 20 amps, Automatically recycles until overload is
removed.
4.
24-VOLT TRAILER RECEPTACLE (M915, M916, M917, and M920). 12-pin connector
for 24-volt power used for Iunette-towed vehicles. (This receptacle is 12-volts on the M917).
5.
OPERATION LAMP SWITCH. With the switch set to NORMAL and the headlamp switch
ON, 12-volt power is supplied to marker lamps, clearance lamps, and 12-volt tractor re-
ceptacle.
6.
CLEARANCE LAMP SWITCH. Provides the capability of flashing the clearance lamps on
the cab and the 12 volt supplied to the tractor receptacle, when switch is depressed and
released. 12-volt power is supplied to the switch when headlamp switch is ON and opera-
tion switch is in NORMAL.
7.
HEAD LAMP SWITCH. Supplies 12-volt power, when in either ON position, through
operation lamp switch in NORMAL, to clearance lamps, marker lamps, and 12-volt tractor
receptacle.
8.
24-VOLT TRAILER RECEPTACLE (M915, M916, and M920). 12-pin connector contain-
ing 24-volt circuit for trailer marker lamps.
9.
12-VOLT TRAILER RECEPTACLE (M915, M916, and M920). Seven-pin connector con-
taining 12-volt circuit for trailer clearance and marker lamps.
10.
CLEARANCE LAMPS. Each unit has a replaceable single-element bulb that illuminates
when headlight switch is in either ON position, and operation lamp switch is in NORMAL.
The clearance lamps will flash when clearance lamp switch is depressed and released.
2-48
