Parasitic draw

  • 1 POST
  • 2006 FORD F-150
  • 109,000 MILES

I have a parasitic drain. It is drawing.56 amps total. When I pull fuses 21(cluster keep alive), 29 and 30(PCM 4x4 power) and 31(radio power) it goes down to.05 amps, which is what I believe it should be. I have been searching for a short, but the wires I have been testing are good so far. Is there something that controls those four circuits that should be telling them to go to sleep. I have the shop electrical book but cannot find anything in common with them.

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Saturday, June 3rd, 2017 AT 9:41 AM

1 Reply

  • 2,537 POSTS

You did not give us enough information about your vehicle like 2 or 4 wheel drive engine size? He is the procedure for the drain test and verify you have given vehicle time to sleep. After removing fuse the amperage does go down then reinstall the fuse and unplug the component it controls like for example the radio. If unplugging the radio makes the amperage drop then the radio would be faulty.


WARNING: Do not attempt this test on a lead-acid battery that has recently been recharged. Explosive gases may cause personal injury. Failure to follow these instructions may result in personal injury.

CAUTION: To prevent damage to the meter, do not crank the engine or operate accessories that draw more than 10A.

No factory-equipped vehicle should have more than a 50 milliamps (mA) or 0.050 amp draw.
Many electronic modules draw 10 mA (0.010 amp) or more continuously.
Use an in-line ammeter between the negative battery post and its respective cable.
Typically, a drain of approximately 1 amp can be attributed to an engine compartment lamp, glove compartment lamp, or an interior lamp staying on continually. Other component failures or wiring shorts are located by selectively pulling fuses to pinpoint the location of the current drain. When the current drain is found, the meter reading falls to an acceptable level. If the drain is still not located after checking all of the fuses, it is due to the generator.
To accurately test the drain on a battery, an in-line ammeter must be used. Use of a test lamp or voltmeter is not an accurate method due to the number of electronic modules.
Check for current drains on the battery in excess of 50 mA (0.050 amp) with all of the electrical accessories off and the vehicle at rest for at least 40 minutes. Current drains can be tested with the following procedure:

Make sure the central junction box (CJB) is accessible without turning on the interior or the underhood lights.
Drive the vehicle at least 5 minutes and over 48 km/h (30 mph) to turn on and activate the vehicle systems.
Allow the vehicle to sit with the key OFF for at least 40 minutes to allow the modules to time out/power down.
Connect a fused (10A) jumper wire between the negative battery cable and the negative battery post to prevent modules from resetting and to catch capacitive drains.
Disconnect the negative battery cable from the negative battery post without breaking the connection of the jumper wire.
NOTE: It is very important that continuity is not broken between the negative battery cable and the negative battery post when connecting the meter. If this happens, the entire procedure must be repeated.
Connect the battery tester between the negative battery cable and the post. The meter must be capable of reading milliamps and should have a 10 amp capability.

NOTE: If the meter settings need to be switched or the test leads need to be moved to another jack, the jumper wire must be reinstalled to avoid breaking continuity.
Remove the jumper wire.

Amperage draw varies from vehicle to vehicle depending on the equipment package. Compare to a similar vehicle for reference.
No factory-equipped vehicle should have more than a 50 mA (0.050 amp) draw.
Note the amperage draw.

If the draw is found to be excessive, remove the fuses from the CJB 1 at a time and note the current reading. Do not reinstall the fuses until you have finished testing. To properly isolate each of the circuits, all of the fuses may need to be removed and install 1 fuse, note the amperage draw, then remove the fuse and install the next fuse, until all of the circuits are checked. When the current level drops to an acceptable level after removing a fuse, the circuit containing the excessive draw has been located.
Check the wiring diagrams for any circuits that run from the battery without passing through the CJB. If the current draw is still excessive, disconnect these circuits until the draw is found. Also, disconnect the generator electrical connections if the draw can not be located. The generator may be internally shorted, causing the current drain.

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Sunday, June 4th, 2017 AT 7:28 PM

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