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Home >> Mercury >> 2008 >> Milan Base, 3.0 1, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 483 (Charging System - General Information - F250-F550 Super Duty) >> Diagnosis And Testing >> Charging System - Dual Generators >> Component Tests >> Generator On-Vehicle Test - Load Test

Generator On-Vehicle Test - Load Test

WARNING: This page is about a different car, the 2006 Ford Pickup, 2006 Ford F550 Super Duty, 2006 Ford F450 Super Duty, and 2006 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
  1. Switch the tester to the ammeter function.
  2. Connect the positive and negative leads of the tester to the corresponding battery terminals.
  3. Connect the current probe to the generator B+ output terminal, circuit 1119 (RD) (upper) / circuit 36 (YE/WH) (lower).
  4. NOTE: Make sure to disconnect the generator that is not being tested.
    Fig 1: Generator Output Graph - 4G (Lower), 75/120 Amps
    G04645489Courtesy of FORD MOTOR CO.
    Fig 2: Generator Output Graph - VR42 (Upper), 95/140 Amps
    G04645490Courtesy of FORD MOTOR CO.
  5. With the engine running at 2,000 RPM, adjust the tester load bank to determine the output of the generator. The generator output should be at or greater than the applicable graphs below. If not, refer back to the pinpoint test or GO to SYMPTOM CHART  for the diagnostic procedures.

    4G (Lower), 75/120 amps 

    VR42 (Upper), 95/140 amps 

  6. With the engine running, turn the A/C on, (if equipped) the blower motor on HIGH and the headlamps on high beam.
  7. Increase the engine speed to approximately 2,000 RPM. The voltage should increase a minimum of 0.5 volt above the base voltage.
    • Backprobe the I circuit at the generator connector (connector plugged in) and measure the I circuit voltage. If the voltage is less than 2 volts, install a new generator. Refer to GENERATOR AND REGULATOR .
    • If the voltage does not increase as specified, refer back to the pinpoint test or GO to SYMPTOM CHART  for the diagnostic procedures.
    • If the voltage increases as specified, the charging system is operating normally. Carry out the Generator On-Vehicle Tests - No-Load Test below.