Tools Required
J 38758 Parasitic
Draw Test Switch Tool
Notice: Do not turn the parasitic draw test switch to the OFF position with
the engine running. Damage will occur to the vehicle's electrical system.
Notice: The test switch must be in the ON position when removing the fuses in
order to maintain continuity in the electrical system. This avoids damaging
the digital multimeter due to accidental overloading, such as
a door being opened to change a fuse.
Important: The switch knob on the J 38758
is marked ON and OFF. When the switch knob is in the ON position,
the circuit is closed and electrical current will pass through the switch.
When the switch knob is in the OFF position, the circuit is open and
electrical current will not pass through the switch.
- Disconnect the battery ground (negative) cable from the battery
negative terminal. Refer to
Battery Negative Cable Disconnection and Connection
.
- Install the male end of
the J 38758
to the battery
negative terminal.
- Turn the J 38758
knob to the OFF position.
- Install the battery ground (negative) cable to the female end
of the J 38758
.
- Turn the J 38758
knob to the ON position.
- Road test the vehicle and activate all of the accessories, including
the radio and the air conditioning.
- Park the vehicle. Turn the ignition switch to the OFF position
and remove the ignition switch key.
- Set a digital multimeter to the 10 A scale.
- Connect the digital multimeter to the test switch terminals.
- Turn the J 38758
knob to the OFF position. This allows the current to flow through the digital
multimeter.
- Wait one minute, then check and record the current reading.
• | When there is a current reading of 2 A or less, turn the J 38758
knob to the ON position.
This maintains continuity in the electrical system. |
• | Then, switch the digital multimeter down to the 2 A scale
for a more accurate reading. |
- Turn the J 38758
knob to the OFF position. Wait 10 minutes.
- Check and record the current reading.
Notice: The test switch must be in the ON position when removing the fuses in
order to maintain continuity in the electrical system. This avoids damaging
the digital multimeter due to accidental overloading, such as
a door being opened to change a fuse.
- Note the battery reserve capacity. Refer to
Battery Usage
.
• | Divide the reserve capacity by 4. |
• | Compare this to the multimeter milliampere reading taken in step
13. |
• | The parasitic current drain should not exceed this number. |
• | Example: If a battery has a reserve capacity of 100 minutes, the
current drain should not exceed 25 milliamperes. |
- If the vehicle has an acceptable amount of current drain and the
vehicle battery was weak or failed a load test, check the charging system.
Refer to
Charging System Check
or
Charging System Circuit Description
.
- When the vehicle has an unacceptable amount of parasitic current
drain, remove each fuse one at a time until the current drain falls to an
acceptable level. This will indicate which circuit is causing the drain.
Refer to
Fuse Block Schematics
in Electrical Diagnosis to diagnose exactly which part
of the suspect circuit is causing the parasitic drain. In some cases
a non-fused circuit or component, such as a generator, is the cause of
excessive parasitic current drain.
- Repeat the parasitic current drain test procedure after any repair
has been completed to make sure that the parasitic current drain is at an
acceptable level.
- When the cause of the excessive current draw has been located
and repaired, remove the J 38758
.
- Connect the battery ground (negative) cable to the battery negative
terminal. Refer to
Battery Negative Cable Disconnection and Connection
.
Component
| Current Draw (mA)
| Notes
|
Typical
| Maximum
|
ECM - PCM32U
| 0.5
| 1.0
|
Generator Regulator
| 1.0
| 1.5
|
Chime/MALL
| 1.0
| 1.0
| Only Max Spec Available
|
Remote Keyless Entry
| 1.0
| 1.0
| Only Max Spec Available
|
Radio
| 1.3 - 3.2
| 4.0
|
HVAC A/C Switch
| 1.0
| 1.0
| C67 Only
|
Anti Lock Brake
| 0.5
| 1.0
|
Battery Self Discharge
| 2.5
| 2.5
| @21°C (70°F)
|
|
Total
| 10.7
| 13.0
|