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Battery Electrical Drain/Parasitic Load Test



Battery Electrical Drain/Parasitic Load Test

Safety Precautions
Caution: Always shield eyes and face from battery. Cigarettes, flames, or sparks could cause battery to explode.
Caution: Do not charge battery, use jumper cables or service connections without proper training.
Caution: Do not tip battery or allow acid to contact eyes, skin, fabrics or paint. Acid is highly corrosive. Flush exposed area with water immediately.
Caution: Keep children away from batteries.


Parasitic Load Testing

Small current drains, called parasitic drains, constantly draw current from the battery even with the ignition switch in the OFF position. These parasitic drains can discharge a battery in 4-6 weeks depending on the battery's state of charge and when the vehicle went into storage.


For normal parasitic current drain, refer to individual component parasitic loads. When testing for parasitic current draw, inspect what types of equipment the customer may have had installed on the vehicle. A cellular phone, anti-theft system, navigation system, or any device added that requires constant voltage to retain a memory, will draw current at all times. Take these added accessories into account when testing for parasitic current drain.


Saturn Parasitic Load Test Device

The parasitic load test device (SA9130Z) is used with a DMM. The test device is used to measure parasitic current drain from the battery with the ignition and all accessories OFF. The load tester, constructed with 1 ohm of resistance and a built-in circuit protection device, opens when the current exceeds approximately 1 amp. When the circuit is opened, the user is alerted by a red light-emitting diode (LED) indicator. The parasitic load test device is put into the circuit between the negative battery terminal and the negative battery cable so it effectively becomes a load in series with all other vehicle loads.

Important: The ignition key must be removed from the cylinder before parasitic load testing. The key-minder circuit is activated by the key cylinder switch when the key is in the ignition cylinder, which adds 20 milliamps of current draw.



Important: If the vehicle has a side post battery, the alligator clamp on the parasitic load test device must be connected to the flat pad part on the negative battery cable. Do not connect the alligator clamp to the bolt on the negative battery cable. This will cause incorrect readings. If the vehicle has a top post battery, a top post to side post terminal adaptor must be used.







1. Install the parasitic load tester between the negative cable and negative battery terminal so the 1 ohm resistor of the tester is in series with the battery.
2. Touch the negative battery cable to the negative battery terminal, and hold them together for 20 seconds, then remove the cable from the battery. This will allow the modules on the vehicle to wake up. Verify that the LED indicator on the tester turns OFF and stays OFF.

• If the LED indicator does not stay off, verify that all vehicle accessories are OFF. Try holding the battery cable against the negative terminal again. If the LED indicator remains ON, something is drawing greater than 1 amp of current.

3. Set the DMM to the MILLIVOLT scale.




4. Measure the current across the tester by putting the DMM probes in the 2 terminals on the tester. The reading is obtained in millivolts. This reading is directly converted to milliamps. Should the parasitic load exceed 1 amp, the circuit will open, and the LED indicator on the tester will light. This may indicate that a vehicle accessory is ON.
5. Wait 5 minutes for the modules on the vehicle to go to sleep. The current draw may be greater than 100 milliamps for the first 2-5 minutes, then it should drop to 10-30 milliamps.

• To find the source of excessive load, start removing fuses and modules in a systematic way. When voltage drops across the tester, the circuit or circuits protected by that fuse is the source of current drain. Also remove the fusible link from the generator to test for a voltage drop. If the voltage drop is greater than 2 volts, replace the generator. Repair the circuit and perform the parasitic load test again to verify the repair.




Parasitic Current Drain Testing With an Ammeter

1. Turn the ignition and all accessories OFF and remove the key from the ignition switch.
2. Disconnect the cable from the negative battery terminal.
3. Follow the manufacturers instructions for the DMM or ammeter being used. This could involve plugging leads into different locations on a DMM and changing the scale to read amperage. On some testers you should start on the 10 Amp scale setting, and after verifying that current drain is less than 2 milliamps, set the scale to 200 milliamps or 20 milliamps.
4. Touch the negative battery cable to the negative battery terminal, and hold them together for 20 seconds. This will allow the modules on the vehicle to wake up.
5. While still holding the cable against the battery, connect the ammeter between the negative cable and the negative battery terminal so that it will be in series. Then remove the cable from the battery. Read the parasitic current drain from the battery.
6. Wait 5 minutes for the modules on the vehicle to go to sleep. The current draw may be greater than 100 milliamps for the first 2-5 minutes, then it should drop to 10-30 milliamps.
7. To find the source of excessive load, remove fuses and modules in a systematic way. When the parasitic current draw is reduced to a normal level, the circuit or circuits protected by that fuse is the source of the current drain. Repair the circuit and perform the parasitic load test again to verify the repair.



Typical Parasitic Loads

Typical parasitic load for this vehicle is 10-30 mA after 5 minutes. If the vehicle does not have one of the following components, then subtract the parasitic load of the component for typical parasitic load of the vehicle (10-30 mA) to determine the parasitic load range for the vehicle being tested.





Important: During CD changer initialization, parasitic current draw will fluctuate between 3 mA to 1 A. The initialization period lasts up to a maximum of 90 seconds. After initialization, the CD changer parasitic current draw will stabilize at approximately 3 mA.



If the CD changer door is open and the light is illuminated, the parasitic current draw will be approximately 65 mA. The light will remain ON for 2 minutes. After the light goes out, the CD changer parasitic current draw will stabilize at approximately 3 mA.


Typical Undesired Parasitic Loads

* Stop lamps ON
* Rear compartment lamp ON
* Courtesy lamps ON
* Dome lamp ON
* Reading lamps ON
* Radio ON






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