2-49. INSTRUMENT AND CAB DOME LAMPS.
With the headlamp switch in either ON position, the instrument lamps illuminate. The
dome lamp illuminates whenever the dome lamp switch is ON.
The low air pressure warning lamp on left-hand cluster, clearance lamp on center cluster
and six indicator lamps on the right-hand cluster are described with their respective
circuits in this chapter, That is, the high engine temperature warning indicator is de-
scribed with the cooling system; low oil pressure warning indicator with the oil system,
etc., (see table of contents).
1. LEFT HAND INSTRUMENT CLUSTER, The instrument gage lamps on this panel receive
12-volt power from headlamp switch when it is in either ON position, Each gage contains
its own illumination bulb.
2. CENTER INSTRUMENT CLUSTER. The center cluster contains the tachograph which is
illuminated when the headlamp switch is in either ON position.
3. HEADLAMP SWITCH. Three-position switch with one OFF position and two ON positions,
In either ON position, 12-volt battery power passes through the switch to energize the follow-
ing lamp in this circuit:
Instrument lamps on left-hand instrument cluster.
Clearance switch and tachograph illumination lamps on center cluster.
Switch and functional indicators on right-hand instrument cluster.
Illumination lamps on heater panel.
Illumination lamps on ratio selector.
The headlamp switch has a variable rheostat that allows the operator to adjust the brightness of all
lamps in this circuit by turning the switch knob.
4. RIGHT-HAND INSTRUMENT CLUSTER. The instrument lamps on this cluster receive
12-volt power from the headlamp switch and illuminate the windshield wiper, and wind-
shield washer indicator.
5. ClRCUIT BREAKER (CB-3). Protects electrical components of dome lamp circuit by open-
ing when load exceeds 20 amps. Automatically recycles until overload is removed.
6. DOME LAMP AND SWITCH ASSEMBLY. When the assembly integral switch is ON, the
lamp is energized by 12-volt battery power through circuit breaker (CB-3).
7. HEATER PANEL LAMPS. When the headlamp switch is in either ON position, the lamps
are energized by 12-volt battery power and illuminates the heater control panel.
8. GEAR RATIO SELECTOR LAMP. When the headlamp switch is in either ON position,
the lamp is energized by 12-volt battery power and illuminates the gear ratio selector.