1. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-1 The two horns on this vehicle were finally located under the front bumper. They were not visible until the vehicle was hoisted.

2. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-2 A typical horn circuit. Note that the horn button completes the ground circuit for the relay.

3. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-3 The horn switch is part of a combination switch on some vehicles.

4. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-4 Horns typically mount to the radiator core support or bracket at the front of the vehicle.

5. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-5 An adjusting screw is provided for setting the horn pitch on some horns.

6. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-6 A circuit diagram is necessary to troubleshoot a windshield wiper problem.

7. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-7 The motor and linkage bolt to the body and connect to the switch with a wiring harness.

8. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-8 (a) A typical wiper motor with the housing cover removed. The motor itself has a worm gear on the shaft that turns the small intermediate gear, which then rotates the gear and tube assembly, which rotates the crank arm (not shown) that connects to the wiper linkage. (b) If the brush retainer becomes loose, the wiper motor will stop because the brushes get their ground connection through the retainer and housing.

9. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-9 A typical wiring diagram of a two-speed windshield wiper circuit using a three brush, two-speed motor. The dashed line for the multifunction lever indicates that the circuit shown is only a part of the total function of the steering column lever.

10. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-10 A typical wiring diagram of a three-speed windshield wiper circuit using a two-brush motor, but both a series and a shunt field coil.

11. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-11 A typical wiper motor connector pin chart.

12. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-12 The wiper motor and linkage mount under the cowl panel on many vehicles.

13. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-13 A single wiper arm mounts directly to the motor on most rear wiper applications.

14. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-14 A typical instrument panel–mounted windshield wiper control switch assembly.

15. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-15 The wiper switch attaches to the steering column on many vehicles.

16. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-16 This rain sense wiper system adjusts wiper speed based on the amount of water on the windshield.

17. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-17 Circuit diagram of a rheostat-controlled, electronically timed interval wiper.

18. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-18 Disconnect the hose at the pump and operate the switch to check a washer pump.

19. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-19 Washer pumps usually install into the reservoir and are held in place with a retaining ring.

20. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-20 A typical rain sensing module located on the inside of the windshield near the inside rearview mirror.

21. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-21 The electronics in the rain sense wiper module can detect the presence of rain drops under various lighting conditions.

22. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-22 A typical squirrel cage blower motor. A replacement blower motor usually does not come equipped with the squirrel cage blower, so it has to be switched from the old motor.

23. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-23 If blower motor resistors are defective, replacement resistors are purchased as a unit, as shown.

24. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-24 A typical blower motor circuit with four speeds. The three lowest fan speeds (low, medium-low, and medium- high) use the blower motor resistors to drop the voltage to the motor and reduce current to the motor. On high, the resistors are bypassed. The “high” position on the fan switch energizes a relay, which supplies the current for the blower on high through a fusible link.

25. Diagnosis and Troubleshooting of Automotive Electrical, Electronic, and Computer Systems, Fifth Edition By James D. Halderman © 2010 Pearson Higher Education, Inc. Pearson Prentice Hall - Upper Saddle River, NJ 07458 FIGURE 24-25 Using a mini AC/DC clamp-on multimeter to measure the current draw of a blower motor.