OM3212 08/11 Operator Cab and Controls - Section 32 Page 32-13 Keyswitch Keyswitch (1, Figure 32-6) is a three position (OFF, RUN, START) switch. Starting fluid is extremely volatile and flammable! Use with extreme care. If the truck is equipped with an engine starting aid for cold weather starting, and ambient temperature is below -5°C (23°F), push the engine starting aid switch “in” for three seconds, then release. Turn the key switch to the START position. If the engine does not start, wait at least 15 sec. before repeating the procedure. Do not crank an electric starter for more than 30 seconds. Allow two minutes for the starter motor to cool before attempting to start the engine again.
Severe damage to the starter motor may result from overheating. OFF - Key insertion/withdrawal position When the key slot is in the verti- cal position, the electrical system is off and no electrical devices are energized. Auxiliary Brake Switch Use this key position to stop the engine when it is operating. Auxiliary brake switch (2, Figure 32-6) applies the auxiliary brake. RUN - When the switch is rotated one position clockwise, it is in the RUN position and all elec- trical circuits (except START) are energized. Depress the center button to apply the auxiliary brake. When the switch is ON, the red lamp will illu- minate.
START - With the transmis- sion selector lever in the NEU- TRAL position, rotate the key switch fully clockwise to the START position, and hold this position until the engine starts (see NOTE below). The START position is spring loaded to return to RUN when the key is released. Pull the switch out to release the auxiliary brake; the light will turn off. NOTE: The engine start circuit is equipped with a engine prelube system. A noticeable time delay will occur (while engine lube oil passages are being filled) before starter engagement and engine cranking will begin. The colder the engine oil temperature, the longer the time delay will be.
In addition, if the truck is also equipped with an engine starting aid for cold weather starting, the engine prelube system should be engaged first for 5-10 seconds, or until the starter is engaged, before activating the engine starting aid. When the auxiliary brake switch is activated, full, unmodulated hydraulic brake pressure (or what- ever pressure remains, if the system is failing) is applied to all wheels. In addition, the parking brake is also applied. The operator should not apply the auxiliary brake switch when the truck is moving, except as an emergency measure. NOTE: This switch is for the manual activation of the auxiliary brake circuit by the operator.
The auxiliary brake circuit will apply automatically, if the hydraulic brake pressure decreases below a pre-set value.