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26SI Series Alternator – T7 Identifying Source of Current Draw – Test

  1. Make sure that every electrical component is turned OFF. Make sure that the keyswitch is turned OFF. Make sure that the dome lights are OFF.
  1. Clamp a 9U-5795 Current Probe or 225-8266 Ammeter Tool Gp around the main ground cable. Clamp the tool with the positive side away from the battery. Reset the probe (zero) before clamping the probe around the wire. Use the current probe if the draw is above approximately 2 A. Use the Ammeter if the draw is below approximately 2 A.
  1. Monitor the current and remove fuses and breakers one at a time. Check the current after each fuse (breaker) is removed. After removing a fuse (breaker) and observing the current, reinstall the fuse (breaker). Start with the main fuses (circuit breakers) first, and proceed to smaller circuits.
  1. If a removal of a fuse causes the current to drop, then the problem is in that circuit.
    1. Check if any components on the circuit are ON.
    1. If everything is OFF, disconnect electrical components on that circuit one at a time and monitor current.
    1. After all of the components in that circuit have been disconnected, check the current. If the problem still exists, then check the wiring for corrosion or shorts to ground.

Note: The standard acceptable current draw is 50 mA. A current draw above 50 mA usually indicates a problem. However, some large machines with multiple electronic control modules have a higher acceptable limit. Contact a Caterpillar dealer for more information.