Examkin

Soru

Zorluk: Çok zorStarting and Charging Systems

A technician is diagnosing a vehicle that will not crank and produces no clicking sound when the ignition is turned to the START position. Multimeter testing reveals a resting battery voltage of 12.612.6 volts. During a cranking attempt, the voltage at the starter solenoid 'S' (ignition) terminal measures 12.412.4 volts, the battery voltage remains steady at 12.612.6 volts, and the voltage drop between the negative battery post and the starter casing is 0.10.1 volts. Based on these test results, which of the following is the most likely cause of the failure?

  1. A
    A compromised ground connection between the engine and the chassis
  2. B
    Unacceptable electrical resistance in the ignition switch circuit
  3. An open circuit within the starter solenoid windingsCevap
  4. D
    A severely discharged or internally sulfated battery

Cevap

An open circuit within the starter solenoid windings
The test results indicate that the battery is fully charged (12.6V) and the ignition switch is successfully delivering trigger voltage (12.4V) to the solenoid's 'S' terminal. The casing ground is also excellent (0.1V drop). Because the battery voltage does not dip when the key is turned, no electrical current is flowing. A solenoid that receives proper trigger voltage and ground but draws zero current and fails to click has an internal open circuit in its electromagnetic windings.

Adım Adım Çözüm

1
Analyze the battery's state of charge using the resting voltage.
The resting voltage of 12.6V indicates a fully charged and healthy battery.
This establishes a baseline, ruling out a dead battery as the initial power source failure.
2
Analyze the circuit current flow during the starting attempt.
The battery voltage remains steady at 12.6V when the key is turned to START.
Because the voltage does not drop, it proves that 0 amps are flowing out of the battery. The starting circuit is completely open and not drawing a load.
3
Evaluate the ignition control circuit (the trigger wire).
The solenoid's 'S' terminal receives 12.4V.
This confirms the ignition switch, relay, and associated wiring are correctly delivering the trigger signal to the solenoid.
4
Evaluate the starter motor's ground path.
The casing shows a 0.1V drop during the start attempt.
A reading of 0.1V is well within specifications (typically under 0.2V for grounds), confirming the physical ground connection to the engine block is excellent.
5
Synthesize the findings to pinpoint the exact component failure.
The starter solenoid has an internal open circuit.
The solenoid receives the required voltage and has a proper ground, but does not click or draw any current, proving its internal electromagnetic windings are broken.

Anahtar Kavram

Voltage Drop Diagnostic Testing and Starting Circuit Logic
Bu soruyu puanla

Konular

Starting and Charging Systems

Bu konudan daha fazla soru