New Products

Home

Our Team

Self Study
Kit

Test
Procedures

 

  

Quick-Check
Starting/Charging Test Procedures

To quickly check Battery Connections we recommend the following:

Voltage Drop Testing - Overview

  • A resistance (ohms) measurement does not tell us the maximum current (amperage) that can pass through a wire/cable or connection.

  • We can test the voltage at the beginning of the wire and compare that voltage with the voltage at the other end of the wire while the circuit is under load (working) to learn if enough current can pass through that part of the circuit.

  • The voltage lost due to overcoming resistance in the wire/cable or connection is called "voltage drop".

  • Loose or corroded connections and undersized or frayed cable can reduce the amount of current that can flow, resulting in hard starting and low battery.

Voltage Drop Test
Negative (Ground) side of Battery

To measure voltage drop from the battery negative post to the cable connection at the engine block:

  1. Set DMM to measure DC Volts (lowest range).

  2. Disable ignition or fuel so the engine will crank but not run.

  3. Connect the black COM lead probe tip to the negative (-) battery post.

  4. Connect the red Volts lead probe tip to the engine block.

  5. Observe the meter reading while cranking the engine.

  • Reading should not exceed 0.2 volts.

Allow a drop of 0.1 volt for each cable connection.

  • A high reading indicates a poor connection.

Poor connections usually respond to a thorough cleaning - poor wires should be replaced.

Quick-Check
Starting/Charging Test Procedures

To quickly check the Voltage Regulator we recommend the following:

 

Regulated Operating Voltage Test

To verify that the voltage regulator is operating properly and is not over charging or undercharging the battery:

  1. Set DMM to DC Volts (range closest to 14 volts).

  2. Connect black COM lead probe tip to battery negative (-) terminal.

  3. Connect red Volts lead probe tip to battery positive (+) terminal.

  4. Verify that battery is fully charged.

  5. Start engine.

  6. Accessories OFF, run engine at idle. Be sure engine is at operating temperature.

  7. Voltage reading should be a least 13.1 volts and no higher than 14.2 volts.

  • Low voltage - check for poor connections, slipping drive belt, faulty regulator.

  • High voltage - usually indicates a faulty regulator.

 

Be sure to visit ALL the new pages of our site

  • New Products
  • Labscope Coach™
  • Driveability Testing Tips
  • Labscope Setups
  • DMM Tests
    		•
    		 

    Contact Automotive Scope Applications
    Automotive Test Products Training
    and Sales Center
    for advanced, instrument specific
    Labscope Operator Training,
    Labscope Driveability Training
    Call 888/717-1333
    or e-mail qbqs@aol.com

    | Next | Test Index | Back |