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Parasitic drain question


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DangerDan
New User

May 10, 2020, 12:28 PM

Post #1 of 4 (284 views)
Parasitic drain question Sign In

I have a 2006 Hummer H3 5 cylinder with about 133,000 miles. The car has an aftermarket radio, subwoofer, and amp.

I noticed revently (Because the car was sitting a few days) that I had a parasitic draw on the battery so I tested it and here are the numbers. The battery is 3 years old and only holds 12 volts but I had it tested and they said it was good. I pulled off the negative terminal and checked the amp draw between the terminal and the battery stump. I know there will be some draw (.05A is acceptable), but I was reading .14A. I started pulling fuses and found that the RDO was pulling .01A which I think is ok. The Aux power 2 is pulling .05A which I think is due to the sound system in the car but is that normal? Last but not least, the BCM was drawing .06A. Does that mean my BCM is bad and is this something an amature mechanic can handle fixing? any info is greatly appreciated.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 10, 2020, 12:36 PM

Post #2 of 4 (278 views)
Re: Parasitic drain question Sign In

Sounds to me like you never let the timers expire.

Here is the proper procedure.

You will need a digital ammeter and a jumper wire with clips on the ends to do this.
First rig any door switches so you can have a door open without triggering the interior lights and unplug the hood light. Remove one battery cable and attach the meter in series between the battery cable and battery post. Take the jumper wire and also attach it the same way. Leave the jumper wire on for at least 30 to 40 minutes to expire all the automatic timers. Now remove the jumper wire and read the meter. Anything over 50ma is too much draw. The way you locate this is to start removing fuses one at a time until the meter drops to normal level. This will be the circuit with something staying on. Determine what components are part of that circuit and check them individually until the problem is isolated.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



DangerDan
New User

May 10, 2020, 5:16 PM

Post #3 of 4 (268 views)
Re: Parasitic drain question Sign In

thanks for the input!. I did wait for the car to "go to sleep" before I took my reading (it goes from .75 to .14) and I followed the exact procedure you stated except for the jumper cables. I found the big power draws to be the BCM and auxiliary power 2 fuses. my question is could a new battery fix this and is .06 amps too much of a draw for the BCM. Also I will try the jumper cables tomorrow.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

May 10, 2020, 5:22 PM

Post #4 of 4 (264 views)
Re: Parasitic drain question Sign In

No, a battery isn't going to change that although it probably needs one.

That reading is slightly high but shouldn't be a problem if driven regularly.

I'm betting if you waited a little longer it would go down even further. I've had vehicles that took 45min to an hour to totally reset all timers.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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