The term parasitic load refers to electrical devices that continue to use or draw a small amount of current after the ignition switch is turned to the OFF position. This small amount of continuous battery draw is expressed in milliamperes (mA). On many new vehicles additional current draw can continue for up to 20 minutes after the ignition is switched OFF. If the parasitic load exceeds normal specifications, the vehicle may die and the vehicle will not start in a day or two. Normal parasitic load is about 50 mA (0.050 amps)
The following includes a test procedure for checking parasitic loads to completion. A brief overview of a suggested test procedure is included along with some typical load specifications:
General Information:
Caution: Always turn the ignition off when connecting or disconnecting the battery terminal cable(s), battery chargers or jumper cables.
Note: Memory functions of various accessories must be reset after the battery is reconnected. If the vehicle’s radio has theft code protection, make sure the code number is available.
Note: In order to perform this test, you must obtain a battery disconnect tool first. This tool can be found at any auto parts retail store or auto parts distributor.
The battery circuit must be opened to connect test switch (shunt) and ammeter (multimeter) into the circuit. When a battery cable is removed, timer circuits within the vehicle computer are interrupted and immediately begin to discharge. If in doubt about the condition of the ammeter fuse, test it with an Ohmmeter prior to beginning the test. An open fuse will give the same reading as no parasitic current drain.
Begin the test with the meter installed and on the scale set to 10 Amps. Select the lower scale to read the parasitic current draw.
Test Procedures Using Disconnect Tool:
Turn the Ignition OFF. Remove the Negative battery terminal. Install the disconnect tool’s male end to the Negative terminal of the battery.
Turn the test switch knob to the OFF position (current through meter) on the test tool. Install the Negative battery cable to the female end of the disconnect tool.
Turn the test switch knob to the ON position (current to switch), road test the vehicle with the vehicle’s accessories on (radio, A/C, etc.).
After the road test, turn the ignition to the OFF position and remove the key. Connect the ammeter terminals to the test switch terminals
(See Figure 1) and select the 10 Amp scale.
Turn OFF all electrical accessories. Turn OFF interior lights, under hood lamps, trunk light, illuminated entry, etc. to avoid damaging the ammeter or obtaining a false reading. All accessories must be turned OFF before turning the test switch knob to the OFF position.
Turn test switch to the OFF position to allow current to flow through the ammeter (multimeter). If the meter reads the wrong polarity (no reading), turn the test switch knob to the ON position and reverse the test leads of the ammeter (multimeter). Turn the switch knob to the
OFF position and observe the current reading. If the reading is less than 2 Amps, turn the switch knob to ON to keep electrical circuits powered-up. Select a lower amperage scale. If necessary switch test leads to the correct position. Turn the test switch to the OFF position and observe the current reading. If the current draw is unusually high, remove accessory fuses until the current draw returns to normal.
See Parasitic Load Table below:
Parasitic Load Table
(All values are in milliamperes)
Component
Anti-Theft System (not keyless)
AutoCommand
Keyless Entry
Body Control Module
Central Processing Unit
Electronic Control Module
Electronic Level Control
Heated Windshield
HVAC Power Module
Illuminated Entry
Light Module
Oil level Module
Multifunction Chime
Normal
0.4
15.0
10.0
3.6
1.6
5.6
2.0
0.3
1.0
1.0
0.5
0.1
1.0
Maximum
1.0
30.0
30.0
12.4
2.7
10.0
3.3
0.4
1.0
1.0
1.0
0.1
1.0
Information compliments of Mitchell.
DesignTech disclaims any liability or responsibility arising out of any inaccuracies of this information or use of this information for installations or otherwise.
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DesignTech International, Inc.
DesignTech International, Inc.
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