TM 9-2320-273-20
2-46. TURN SIGNAL AND HAZARD WARNING LAMPS.
When the operation lamp switch is in NORMAL position, battery power is applied to the turn signal
control to illuminate right or left: front turn signals, rear turn signals as well as trailer turn signals
on M915, M916, M917, and M920 vehicles through tractor-mounted receptacles. Also, the turn
signal control contains a hazard warning switch, that allows the operator to flash all lamps in the
turn signal system simuItaneously.
1.
MARKER AND TURN SIGNAL LAMP ASSEMBLY. Each assembly has a replaceable
single filament bulb that flashes when turn signal control or hazard warning switch is on.
2.
RELAY (K2). Normally open contacts; closed by 12 volts from left turn signal control or
hazard warning switch. When relay is energized, 24 volts is applied to tractor mounted
receptacles for trailer left turn signals.
3.
RELAY (K3). Normally open contacts; closed by 12 volts from right turn signal control or
hazard warning switch. When relay is energized, 24 volts are applied to tractor mounted
receptacles for trailer right turn signals.
4.
ClRCUIT BREAKER (CB-2). Protects electrical components of flasher, turn signal control,
and hazard warning switch circuits by opening when load exceeds 20 amps. Automatically
recycles until overload is removed.
5.
ClRCUIT BREAKER (CB-7). Protects electrical components of 24-volt relay and circuits
by opening when load exceeds 20 amps. Automatically recycles until overload is removed.
6.
OPERATION LAMP SWITCH. Two-position switch for normal and blackout modes of
operation. When set to NORMAL, 12-volt battery power from circuit breaker (CB-2)
passes through switch contacts to turn signal control, flasher unit, and hazard warning switch.
7.
REAR TAIL LAMPS. Each assembly contains two bulbs; the tail lamp turn signal and
stop lamp circuits all use the same bulb. When either the turn signal control or hazard
warning switch are on, the turn signal and stop lamp filaments flash. When the turn signal
control is activated, only the bulb on the side selected flashes. If the brakes are engaged at
the same time that the hazard warning switch is on, both bulbs flash. When the brakes are
engaged and the turn signal control is activated, one bulb will flash and the other bulbs will
remain on constantly.
8.
24-VOLT TRAILER RECEPTACLE (M915, M916, M917, and M920). Tractor mounted
12-pin connector provides 24 volts power to Iunette-towed vehicles. This receptacle is
12-volts on the M917.
9.
FLASHER UNIT. This unit receives 12-volt power from operation lamp switch in NORMAL
position and supplies this power alternately on and off to turn signal control or hazard
warning switch when either one is engaged.
10.
HAZARD WARNING SWITCH. When this switch is engaged, it receives 12-volt power from
the operation lamp switch and energizes all components in the turn signal circuits simulta-
neously.
11.
TURN SIGNAL CONTROL. When this control is engaged, it receives 12-volt power from
flasher unit. (The flasher unit receives 12-volt power through operation lamp switch and
circuit breaker CB-2.) Power is then supplied to:
a.
Front left or right turn signals.
b.
Rear left or right turn signals.
c.
12-volt Trailer Receptacle.
d.
Relays K2 and K3 (To energize relay and supply power to both tractor mounted
24-volt receptacles for trailer turn signals.)
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