Disadvantage: Could be difficult to use depending on connector/part location; How it is connected into the circuit is critical; has the potential of damaging the circuit.
• Because of the potential for accidental short-to-grounds when using a jumper wire, be sure to follow the EWD and plan the placement of the jumper carefully, never by-passing a load! If available, use a fused jumper wire.
• Never by-pass a resistor in a circuit. Components, such as fuel injectors, can have a series resistor which limits current flow through the injector solenoid coils. Shunting around that resistor could cause significant damage.
Diagnosing Parasitic Load Problems
A parasitic load continuously draws current from the battery, even when the key is OFF. With the introduction of ECU's that have a "memory", a small parasitic load of up to 50 mA is considered acceptable. You will find the average parasitic load to be around 20 mA or less, depending on the vehicle.
If the customer complains of a dead battery after the car is parked for a day or two (and the charging system/battery are OK), an unwanted parasitic load could be the cause. These excessive parasitic loads are usually caused by a short circuit condition where the control of the circuit (such as a switch) is bypassed, causing the load to be ON all the time.
Isolating a parasitic load problem is a matter of disconnecting various fuses, junction blocks, wire harness-to-wire harness connectors, and individual connectors or pins (applying a strategic process of elimination). This process can be broken into two parts:
• Isolate the fuse which "feeds" the parasitic load
• Determine which individual circuit has the problem by disconnecting connectors fed by that fuse.
Verify the Problem and Isolate the Fuse
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