DriveMaster® - Lesson 4: Electrical Control Systems (NON-ECM), © 2001 Horton, Inc.

	LESSON 4: ELECTRICAL CONTROL SYSTEMS (NON-ECM)

	4.1 Types of Electrical Control Systems		INDEX
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	The electrical wiring that controls the fan drive varies from one vehicle to another, but generally will be one of three types of systems: Normally-Open Normally-Closed ECM controlled Most newer engine designs are ECM controlled. Manufacturers that tend to have normally-closed electrical controls include: Blue Bird GMC Mack Ford International White GMC Manufacturers that tend to have normally-open electrical controls include: Freightliner Mack Western Star Kenworth Volvo Peterbilt The fan drive electrical control system may be normally-open or normally-closed, and the solenoid valve may be plumbed to work in either system. Horton DriveMaster fan drives are plumbed as follows: for a normally-open electrical system, connect the air supply to the normally-open port of the solenoid valve. for a normally-closed electrical system, connect the air supply to the normally-closed port of the solenoid valve. The commonly-used term "normally-open system" refers to an electrical system. The commonly-used term "normally-open valve" refers to the pneumatics of the valve.		Learning Objectives: • Describe the basic operation of normally-open and normally-closed control systems. • Describe how solenoid valves should be plumbed in a normally-open or normally-closed system.
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INTRO | LESSON 1 | 2 | 3 | 4 | LAB | REVIEW | SERVICING | LESSON 5 | 6 | 7 | 8 | 9 | 10 | 11 | REVIEW | TEST