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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 101 (Battery, Charging System And Starting System) >> Diagnostic Information and Procedures >> Battery Electrical Drain/Parasitic Load Test >> Load Test

Load Test

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Refer to Battery Disconnect Caution .
NOTE: Do not turn the parasitic draw test switch to the OFF position with the engine running. Damage will occur to the vehicle's electrical system.
NOTE: The test switch must be in the ON position when removing the fuses in order to maintain continuity in the electrical system. This avoids damaging the digital multimeter due to accidental overloading, such as a door being opened to change a fuse.
IMPORTANT: The switch knob on the J 38758  is marked ON and OFF. When the switch knob is in the ON position, the circuit is closed and electrical current will pass through the switch. When the switch knob is in the OFF position, the circuit is open and electrical current will not pass through the switch.
  1. Disconnect the battery negative cable from the battery negative terminal. Refer to Battery Negative Cable Disconnection and Connection .
  2. Install the male end of the J 38758  to the battery ground terminal.
  3. Turn the J 38758  knob to the OFF position.
  4. Install the battery negative cable to the female end of the J 38758  .
  5. Turn the J 38758  knob to the ON position.
  6. Road test the vehicle and activate ALL of the accessories, including the radio and air conditioning. This may take up to 30 minutes.
  7. Park the vehicle. Turn the ignition switch to the OFF position and remove the ignition switch key.
  8. Connect a 10A fused jumper wire to the test switch tool terminals.
  9. Turn the J 38758  knob to the OFF position. The current now flows through the jumper wire.
  10. Wait 1 minute. If the fuse blows, install an inductive ammeter and go to step 19.
  11. Remove the fused jumper wire.
  12. Set a digital multimeter to the 10A scale.
  13. Connect the digital multimeter to the test switch tool terminals.
  14. Turn the J 38758  knob to the OFF position. The current flows now through the digital multimeter.
  15. Wait 1 minute. Check and record the current reading.
    1. When there is a current reading of 2A or less, turn the J 38758  knob to the ON position. The electrical current will now pass through the switch.
    2. Then switch the digital multimeter down to the 2A scale for a more accurate reading when the J 38758  knob is turned OFF.
  16. Turn the J 38758  knob to the OFF position. Wait 15 minutes for most vehicles.
  17. Check and record the current reading.
  18. Note the battery reserve capacity, amp hour rating. Refer to Battery Usage .
    1. Divide the reserve capacity by 4, amp hour rating by 2.4.
    2. Compare this to the multimeter milliampere reading taken in the previous step. The parasitic current drain should not exceed this number. Example: If a battery has a reserve capacity of 100 minutes, (60 A/H) the current drain should not exceed 25 mA.
  19. If excessive current drain is not found at this time and there are no other apparent causes, complete the following:
    1. Using the MIN/MAX function of the digital multimeter, monitor the parasitic drain overnight or during the day. This will determine if something has been activated during that time frame.
      2. NOTE: The test switch must be in the ON position when removing the fuses in order to maintain continuity in the electrical system. This avoids damaging the digital multimeter due to accidental overloading, such as a door being opened to change a fuse.
      IMPORTANT: Removing fuses, relays, and connectors to determine the failure area may wake up modules. You must wait for these modules to go to sleep or use the sleep function on the scan tool.
    2. When the vehicle has an unacceptable amount of parasitic current drain, remove each fuse one at a time until the current drain falls to an acceptable level. This will indicate which circuit is causing the drain. Refer to Power Distribution Schematics to diagnose exactly which part of the suspect circuit is causing the parasitic drain. In some cases a non-fused circuit or component, such as a relay, is the cause of excessive parasitic current drain.
    3. Repeat the parasitic current drain test procedure after any repair has been completed to make sure that the parasitic current drain is at an acceptable level.
    4. When the cause of the excessive current drain has been located and repaired, remove the J 38758  .
  20. Connect the battery negative cable to the battery negative terminal.
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