Good Sam Club Open Roads Forum: Mystery Battery Draw While Parked UPDATE
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 > Mystery Battery Draw While Parked UPDATE

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BFL13

Victoria, BC

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Posted: 01/10/22 10:07am Link  |  Quote  |  Print  |  Notify Moderator

Update 13 Jan--
-----------

Never know--somebody on here might have an idea what to look for, thanks for any help.

2003 Chev 2500HD LT (so has lots of electrical stuff that works with ignition off) 6L gas.

Problem is the battery voltage goes down too fast while engine off parked overnight. Say 12.6 evening then 12.5 next morning then 12.4 next morning, etc.

In theory you can find a mystery draw by pulling fuses one at a time, but there are a kazillion fuses, so it would be helpful to know some likely suspects as nothing appears to be "on" when left overnight.

I took one cable off the battery inserted meter and confirmed there is a steady 0.74 amp draw. I don't know what is a normal amount but this seems high at 18AH a day.

I had the battery load tested and it was in excellent shape with a 400 amp draw and bounced right back. I charged it up and let it sit and it has no unusual self-discharge after a few days. So it is not the battery, it must be a mystery draw AFAIK.

I cannot relate when this started to anything that happened. Years past ISTR it would sit at about 12.5v for long periods while parked. It has been kept plugged in at home mostly with the camper on so the engine battery has been floating at 13.x volts, so I can't say when this all started. Notice it now with the camper off.

The battery dash light glows dimly with ignition off, but it has done that for 19 years. The dash shift indicator lamp is out, which is fairly new- can't see what gear you are in.

So what are some likely suspects that I could check by pulling their fuses or circuit breakers?

* This post was edited 01/13/22 10:54am by BFL13 *


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aftermath

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Posted: 01/10/22 10:29am Link  |  Quote  |  Print  |  Notify Moderator

Here is what I was told by my local Acura dealer mechanic. We had a new RDX that needed a battery replacement within the first two years. We parked it in our locked garage each night and usually did not lock it up. He said that when just sitting there, many sensors are still functioning like the proximity sensors. He told us to lock it each night, thus turning some of the sensors off, thus protecting the battery. I really don't know if this is true or not but we always lock the car and the truck each time we leave.
People typically drive their vehicles EVERY day, so charging occurs regularly. When you park one that isn't driven much, this really can become an issue. I hardly drive my truck, it sits for long periods of time.


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Ed_Gee

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Posted: 01/10/22 10:31am Link  |  Quote  |  Print  |  Notify Moderator

It may be tedious but I'd start removing fuses, one at a time, check current draw after each fuse removed ... reinstall the removed fuse and move on.


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Posted: 01/10/22 10:35am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:



The battery dash light glows dimly with ignition off, but it has done that for 19 years.


I'd start with the problem that you've neglected for 19 years. But that's just me.


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otrfun

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Posted: 01/10/22 10:46am Link  |  Quote  |  Print  |  Notify Moderator

A clamp-on DC ammeter may make your troubleshooting a bit more efficient. Some will read down to .1 - .2a relatively accurately and will allow you to check current on a number of wires/cables very quickly. I've troubleshot similar problems as yours and was able to find the source of the problem with just a couple of random wire/cable checks with a clamp-on.

Also, don't know about your Chevy, but when you open the hood or door on our Ram, it temporarily activates portions of the BCM with a several amp load. This load disappears after 5-10 min. Just something to keep in mind so you don't find yourself wasting time chasing phantom draws.

Good luck!

pianotuna

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Posted: 01/10/22 11:11am Link  |  Quote  |  Print  |  Notify Moderator

How old is the battery?


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BobsYourUncle

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Posted: 01/10/22 11:42am Link  |  Quote  |  Print  |  Notify Moderator

Don't rule out the alternator.

While it may appear fine, charge well etc, a bad diode in the rectifier bridge can cause an undetectable "leakage".

I had that once in an old car. The battery would run flat after sitting a few days. I had a dickens of a time figuring it out until I disconnected the alternator and found no drain with it unplugged, and the main battery wire removed. Took it apart, replaced the rectifier assembly - end of problem.


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ktmrfs

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Posted: 01/10/22 12:00pm Link  |  Quote  |  Print  |  Notify Moderator

there is one VERY important detail about car battery draw with ignition off.

THE VEHICLE GOES THROUGH A SHUTDOWN PROCEDURE ONCE IGNITION IS TURNED OFF. THAT PROCEDURE TAKES TIME AND IS SPECIFIC ON WHAT IS GOING ON.

Trying to measure battery draw before shutdown has actually occurred is IMHO a way to go down a rabbit hole.

So. First, it usually takes 20 minutes or so before it is in full shutdown so checking draw before that is pretty much useless.
Next, for the shutdown to start it usually requires that key is out of ignition, ALL doors, HOOD, trunk, Windows are closed........ get the picture on the next issue.... how to I measure current w/o access to the battery.....


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BFL13

Victoria, BC

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Posted: 01/10/22 12:34pm Link  |  Quote  |  Print  |  Notify Moderator

Lots of good info I didn't know, thanks! More ideas welcome.

On that last one, I can use longer leads on my meter with clamps to insert between the neg post and the neg wire terminal, passed out under the hood with the hood down so I can read the meter (10 amp limit type) from outside.

Raining out now, so will wait on that. Also to check what our 2015 van has for a draw to compare with that 0.74 amp the truck has.

Worst case I can leave it plugged in on a battery maintainer like I do with the engine batt in the Class C. The truck is ok to drive around during the day, battery stays up. Just can't leave it parked for a few days anymore.

jdc1

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Posted: 01/10/22 12:43pm Link  |  Quote  |  Print  |  Notify Moderator

BC is VERY cold. Would the severe cold weather be doing it? Loads? Memory in computers and radio. Do you have an alarm you turn on? That's another parasitic load.

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