CM850 Electronic Control System – 019-274   Intermediate Speed Control 1 Switch

The Intermediate Speed Control is a fixed engine speed governor that can be activated by up to three switches. When activated, the intermediate speed control feature governs engine speed to the corresponding preset speed depending on the priority of individual intermediate speed control inputs and also of the main accelerator.

If INSITE™ electronic service tool is available, monitor the switch for proper operation. If not, follow the troubleshooting procedures in this section.

Locate the desired ON/OFF toggle switch. Remove and tag the two connectors from the terminals on the switch. Touch the multimeter probes to the terminals on the switch.

Move the switch to the OFF position and measure the resistance. The multimeter must show an open circuit (100K ohms or more).

If the circuit is not open, the switch has failed. Refer to the OEM troubleshooting and repair manual for the replacement procedures.

Move the switch to the ON position and measure the resistance. The multimeter must show a closed circuit (10 ohms or less).

If the circuit is not closed, the switch has failed. Refer to the OEM troubleshooting and repair manual for the replacement procedures.

If the resistance value is correct, the switch must still be checked for a short circuit to ground.

Touch one of the multimeter probes to one of the switch terminals. Touch the other probe to chassis ground. Move the switch to the ON position and measure the resistance. The multimeter must show an open circuit
(100K ohms or more). If the circuit is not open, the switch has failed. Refer to the OEM troubleshooting and repair manual for replacement procedures. If the switch passes all of the previous checks, the circuit must be checked for an open circuit, a short circuit to ground, a short circuit from pin to pin, and a short circuit to an external voltage source.