Lesson 3:QUiCK TESTING

Learning objectives: 

at the end of the lesson you must be able to:

1. Describe the purpose and importance of quick testing in diagnosing starting system issues.

2. Respect the importance of accurate diagnosis before replacing starting system components.

Purpose and Importance in Diagnosting Starting System

No crank with no headlights

Dead Battery(corroded terminals)

 or an open in electrical circuit.

Burned fuse 

Burned or broken wire 

Head lights go out when cranking

Indicates heavy current draw.

Battery may be weak.

Starter motor may be shorted.

Lights stay bright but, no crank

High resistance or an open in starting circuit 

Possibly Ignition switch

Wiring , solenoid, cable connections, relay, fuse 

Current Draw Test most of the starters draw over 200 Amps 

Hookup the VAT

Disconnect Fuel/ignition

Crank engine for 5-10 seconds and note the voltage.

Load the battery until same voltage is obtained

  and record the Amp.

The Amps will equal the current drawn by

  the starting motor.

Voltage Drop Test checks for high resistance across a cable/connection

• Disable ignition/fuel

• Hook voltmeter between +ve battery post and +ve starter terminal

• Hook voltmeter between -ve battery post and starter ground.

• Crank the engine (5-10Sec.), Voltmeter should not read more

 then 1volts.

If greater:

• Loose electrical connections.

• Burned or pitted solenoid contacts 

SUMMARY oF THE TOPIC

Voltage drop testing in a starting system is a diagnostic method used to identify excessive resistance in the electrical circuits that can affect performance. This test measures the difference in voltage between two points in a circuit while the system is under load, typically during engine cranking. A significant voltage drop indicates poor connections, corroded terminals, damaged wires, or internal resistance in components like the starter motor or solenoid. By testing both the positive and ground sides of the starting circuit, technicians can pinpoint the exact location of the voltage loss. This helps ensure that the starting system receives full battery power for efficient engine cranking and reliable operation.