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Doug,,, thank you for calculation,, yes i calculated the same rate of battery discharge,, over a month. Problem is compounded by fact car is only driven 2 miles twice a day,,,, the battery seems to lose 50% of its charge after 2 weeks ??? Battery was tested and replaced twice,, no change.
Alternator does charge at proper voltage (over [email protected]) and does charge-up battery when driven more miles. Never had this problem before with low battery!!!
Thinking further,,,, maybe i'm getting additional battery drain from (defective) alternator too ??
,,,,would a leaky diode still charge battery normally ??
but i still have 75ma constant drain on the BCM fused circuit 1.8A/dayX30=54amps/month !!!!!
and car wont start with very low battery,,, may actually be fewer days than calculated.
Had the car in shop,,, mechanic did verify, but could not identify problem causing low battery,, maybe electrical not his specialty ??? ,,, told me hes been working on cars for 25 years :)
I agree, 30 days at 75mA is 54 amp-hours, enough to kill many batteries.

I think you're on the right track with the BCM fuse. The remaining challenge is to narrow it down from there.

As for "electrical not [being] his specialty", my observation is that, for many, electricity is black magic :) Civil engineers think electrical engineers are spooks. And electrical engineers think RF guys are spooks :) Throw in some encryption, and it gets really scary :)

Seriously, I was never comfortable with it until I got some rigorous schooling in college. Prior to that, everything was a hodge-podge of fuzzy terms - AC, DC, rms, peak, average, continuous, balanced, unbalanced, etc.

So it's understandable that your guy may not be real comfortable with it.

Back to diagnosing the parasitic draw, the challenge at this point is that it becomes tedious. With each test - each removal of a load by pulling a downstream fuse or removing a bulb - the quiescent 75mA load may jump to a different level, either higher or lower. Before you can move to the next text, you will need to re-establish the 75mA draw, which may take a few steps and several minutes of waiting. So it can take a while to narrow it down to the source.

Of course, if you see the 75mA draw drop way down when you remove a load, then you may have found the problem. So perform that test again to confirm it, then shout "eureka!" :)

In short, it can be a grind going thru this looking for the culprit. Some of the hi-end test equipment at the dealer may be helpful. For example, it may be able to communicate with the BCM to find out what's keeping it from dropping to its lowest current draw - ie, going into standby. Most ordinary scanners won't be able to do that. So you're left with disconnecting cables, bulbs, etc, until that 75mA goes away.

That said, I think you're pretty close to finding it. So I encourage you to keep looking.

HTH.

Doug

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Hey everyone, just wanted to let you all know that all this information has been of great use to me. I am currently on the same boat and struggling to figure out the problem. However, my vehicle is randomly draining the batter over night and not over and extended period of time. I do believe my problem may be related to my stereo. Suddenly, there is no sound from the speakers while stereo is on. I've pushed all the buttons changing the stations and going through different functions of the head unit and nothing comes out of the speakers. The next day after this happens, the battery is dead. After jump starting, the vehicle runs as normally would and stereo works just fine. Any ideas as to what this may be?

Thanks!!
 

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Hey everyone, just wanted to let you all know that all this information has been of great use to me. I am currently on the same boat and struggling to figure out the problem. However, my vehicle is randomly draining the batter over night and not over and extended period of time. I do believe my problem may be related to my stereo. Suddenly, there is no sound from the speakers while stereo is on. I've pushed all the buttons changing the stations and going through different functions of the head unit and nothing comes out of the speakers. The next day after this happens, the battery is dead. After jump starting, the vehicle runs as normally would and stereo works just fine. Any ideas as to what this may be?

Thanks!!
What year is your car? Is the head unit stock? Or aftermarket? Is there a factory amp under the rear package try? Did you install an amp?

My first guess would be the amp, aftermarket or factory, is not shutting off when the car does.

Another thought was bad ignition switch. But that doesn't explain the radio not playing when the car is on. Still, I don't want to rule it out yet. A bad switch could have one circuit staying open when it should be closed (-> no sound because no power to amp), or staying closed when it should be open (-> dead battery). I would need to look at some drawings to drill down on this.

Still another thought is wiring. I would inspect any wiring in the rear deck first (where the factory amp is). Look for a loose wire at the connectors or a chafed wire in the area. The idea is that the wire that turns the amp off and on has an intermittent connection or is shorting to ground.

After that, you would need to pull the head unit to inspect the wiring there.

In short, since the radio seems to be misbehaving in conjunction with the dead batteries, I think you're on the right track focusing on the sound system.

Doug

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I had to take my fuse for my radio out it was drawing like 2a..now I'm down to 79ma being drawn from somewhere I took my display fuse out and it went down to 30ma.. i was going to try to ride with that fuse out..I realized none of the gauges work with that out...Has anyone heard about a radio drawing that much..No aftermarket stuff I have a 06 ss with the Bose system kind of getting tried of riding without a radio
 

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I had to take my fuse for my radio out it was drawing like 2a..now I'm down to 79ma being drawn from somewhere I took my display fuse out and it went down to 30ma.. i was going to try to ride with that fuse out..I realized none of the gauges work with that out...Has anyone heard about a radio drawing that much..No aftermarket stuff I have a 06 ss with the Bose system kind of getting tried of riding without a radio
When the radio is off, the only current it draws is for keeping the presets alive and the clock running (w/o display). That takes like 1uA. Call it 10, worst case. So it should be a very tiny draw. BTW, 10uA=0.01mA . Depending on the meter, it might not even show up.

Keep in mind what's been posted earlier in the thread. After making a change, you may need to way a few minutes for everything to die down so you can get the actual standby current.

Doug

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