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Parasitic Load Test

NOTE: Remove ignition key from cylinder before load testing. Key reminder circuit is activated by key cylinder switch when key is in ignition cylinder. This adds 20 milliamps of current draw. Also check for any additional aftermarket equipment, such as an anti-theft system, that may require a constant voltage to retain memory.
  1. Turn ignition and all accessories off. Disconnect negative battery cable. Install an ammeter between negative battery cable and negative battery terminal so that ammeter is in series with other resistances. Read and record parasitic load from battery. If parasitic load is 1.4 amps or more, go to next step. If parasitic load is less than 1.4 amps, check for normal parasitic loads. See NORMAL PARASITIC LOADS  table. If readings do not add up to normal parasitic loads, go to step  3 .
  2. Some models may be equipped with delayed functions, such as a Heating Ventilation Air Conditioning (HVAC) delayed blower function that allows HVAC blower fan to remain on about 50 minutes after ignition has been turned off. Another example of a delayed function is instrument panel drawing 40 milliamps for 20 minutes after ignition has been turned off. To eliminate misdiagnosing a parasitic load do to delayed functions, install a jumper wire between negative battery cable and negative battery terminal. While jumper is installed, connect leads of ammeter to battery cable and negative battery terminal. This puts ammeter in parallel with jumper wire. After 50 minutes, remove jumper wire. Read and record parasitic drain from battery.
  3. Start removing fuses to find source of excessive load. Also remove fusible link located between generator and starter. If current drops across tester when fuse or fusible link is removed, circuit(s) protected by that fuse or fusible link is source of current drain. Repair circuit and retest for parasitic drain. For normal parasitic loads, see NORMAL PARASITIC LOADS  table.
NORMAL PARASITIC LOADS

Circuit Milliamps
Anti-Lock Brake System (ABS) 1.0
Body Control Module (BCM) 1.0-3.5
CD Changer (1) 3.0
Chime/Dome Light Module .7-.9
Fog Light Circuit 6.0
Generator 1.0-2.0
Horn .25
HVAC Delayed Blower Control 1.0
Instrument Panel Cluster (2) 40.0
Powertrain Control Module (PCM) 1.0
Radio 2.8-4.3
Remote Keyless Entry 2.75
(1) If CD changer is activated, parasitic load will fluctuate between 3 milliamps and one amp for up to 90 seconds. CD changer is located in center console inside storage compartment. If CD changer door is opened and light on CD changer is illuminated, parasitic load will be about 65 milliamps for 2 minutes, until light on CD changer turns off.
(2) Current will draw for 20 minutes after ignition switch is turn off.
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