ASE G1 Auto Maintenance and Light RepairElectrical/Electronic SystemsMedium
A vehicle's windshield wipers operate only on the 'HIGH' speed setting, but not on 'LOW' or 'INTERMITTENT'. The washer fluid pump works correctly. What is the MOST likely cause?
- AA blown fuse for the wiper circuit.
- BA faulty wiper motor.
- CA bad wiper switch.
- DAn open circuit in the 'LOW' speed wiring from the switch to the motor.
Show answer & explanationAnswer & explanation
Correct answer: C. A bad wiper switch.
If the wipers work on 'HIGH' speed, the wiper motor, its associated fuse, and the main power/ground are functional. The problem lies in the selection of 'LOW' and 'INTERMITTENT' speeds. The wiper switch is responsible for directing power to different windings or control circuits within the motor for each speed setting. If only 'HIGH' works, it suggests the switch contacts or internal logic for the other settings are faulty.
Why the other options are wrong
- A. A blown fuse would prevent the wipers from working on any speed, or potentially all accessories on that circuit, but the 'HIGH' speed works.
- B. If the wiper motor were completely faulty, it wouldn't work on any speed. If only some windings were faulty, it could be a possibility, but a switch issue is more common for selective speed failure.
- D. An open circuit in the 'LOW' speed wiring would prevent 'LOW' speed from working, but wouldn't explain why 'INTERMITTENT' also fails, as they typically use different control paths or logic within the switch/motor.
Wiper System Speed Control
Wiper motors often have multiple windings or are controlled by a module to provide different speeds, selected by the wiper switch.
- Wiper switches directly control motor windings or send signals to a control module.
- A failure affecting specific speeds but not others often points to the switch.
- Different speeds usually involve different power paths or control signals.
Memory trick: High is fine, other speeds decline, switch is the sign.