CHASSIS CONTROLS AND INDICATORS
Item and Function
AIR CLEANER INDICATOR shows red when engine air filter needs servicing.
PARKING BRAKE WARNING LIGHT lights when parking brake is on.
LOW AIR PRESSURE WARNING LIGHT illuminates when air brake system pressure drops below 50-60 psi (345-
SPRING BRAKE WARNING LIGHT lights when spring brakes are engaged.
LOW COOLANT LEVEL LIGHT (M939A2 series vehicles) lights when engine coolant level is low.
AXLE LOCK-IN LIGHT lights when front wheel drive lock-in switch is on.
HIGH BEAM INDICATOR lights when front headlights are on high beam.
HAND THROTTLE CONTROL sets engine speed at desired rpm without maintaining pressure on accelerator
pedal. Throttle control locks in desired position when pulled out. Rotating control handle clockwise or
counterclockwise unlocks it.
BATTERY SWITCH activates and deactivates all electrical circuits on or off except arctic heater and lights.
IGNITION SWITCH has OFF, RUN, and START positions. Switch automatically returns from START to RUN
when hand pressure is released.
TACHOMETER indicates engine speed in revolutions per minute (rpm) and operating hours in tenths.
SPEEDOMETER/ODOMETER indicates vehicle speed and total mileage.
ENGINE COOLANT TEMPERATURE GAUGE indicates engine coolant temperature. Normal engine coolant
operating temperature for M939/A1 series vehicles is 1750-195°F (790-91°C) and 190°-200°F (880-93°C) for
M939A2 series vehicles.