battery drain

[needbigtruck]

I have a battery drain issue, like some of the threads I searched I pulled fuses and tested for a current draw. Thought I had it nailed when I found a draw for the radio of about 1.8 amps. So I left the fuses pulled. Found I have to put it back even on short trips because it also powers things like speedometer and tach who’d have thought. But after sitting the batteries would be drained again. So I looked some more. Found the battery draw was only for a short time, like 30 seconds and would come back if you opened the door. Must be tied to the circuit that keeps it on for 15 minutes until you open the door. So I looked some more and found about a 2 amp draw on the interior lamps, even though they are off. It doesn’t go away. I could leave that fuse pulled but the door locks and things like that don’t work. So now I am thinking BCM, or bad body to frame grounds. I have read a little about that. It’s too cold to go crawling around under the truck now, so until it’s warm again I leave the batteries disconnected. Does anyone have any good information about fixing a grounding problem, like where they are and is it good enough to just clean the connections or do I need to actually need to replace the ground wires. Thanks

[Dave.H]

By chance what color is the light on your rearview mirror for the onstar? Green or Red?

[DennisG01]

Just out of curiosity, have you checked for current draw right at the battery? Or, are you jumping around from fuse to fuse?

[needbigtruck]

I don't have OnStar. I was checking across each fuse to begin with (that's when I thought the radio was the culprit), but now disconnect both batteries and then hook my ammeter across just one battery. It's easier because I just pull, look at the meter, then put it back in. I also disconnect the hood light and don't start pulling fuses until about 5 minutes after I hook the ammeter up. I haven't done the inside fuses because I keep all the doors closed too.

[Dave.H]

That's why I asked. There are still buttons there though, right? And a light. There have been some people that have found a correlation between that light being red and their battery draining. That may be a newer issue though.


I don't have OnStar. .

[needbigtruck]

I don't have any buttons or lights anywhere associated with On-Star. It must have been an option in 2001 but I wasn't interested in it. Not sure I would want it now either. To bad new vehicles have it automatically whether someone wants it or not.

[needbigtruck]

The saga continues. I’ve disconnected the hood light, both batteries and connected my ammeter across just one battery and left it clipped there over night. When I looked this morning without opening any doors, just the hood the current draw was just .04 amps. Not enough to drain the batteries. So I opened then closed the door and watched. It went up to over 3 amps while the interior lights, then after 15 seconds the lights went out and the current dropped to .9 amps. It stayed there for another 30 seconds and then dropped to .23 amps. I don’t know how long it stays at .23, I watched it for about 5 minutes and it didn‘t change, but overnight something else turns off and the amps drop to .04. I like the amenities that these modern electrical circuits bring, but like many other threads I’m seeing when some little part goes wrong, it’s almost impossible to figure it out.

[JohnC]

If the draw is really only .04 amps, then you may just have a bad battery.

[needbigtruck]

Well I have been thinking that. They are NAPA batteries and only about 2 years old. It seems odd both would fail at the same time. When I get home I disconnect both batteries wait a while and test the voltage. It starts at 12.51 volts. If I leave them disconnected for a couple of days, the voltage drops down somewhere in the neighbor hood of 12.35-12.40 volts on both batteries without any load on them. I guess I'll take a trip to NAPA and see what they say.

[Big Eric]

When I drove semi, I'd get a battery every now and again that would get a "bad cell" in it. It wouldn't hold a charge and it would even draw the other batteries down. You may have a battery with a bad cell in it.

[More Power]

These trucks use what is called "RAP" (Reserve Accessory Power), which does, among other things, keeps the radio on for 10-15 minutes after turning the truck off - or till you open a door, keeps the interior courtesy lamps on for a short period after opening and closing a door, and other stuff. The BCM controls RAP - if I remember correctly.

Jim

[needbigtruck]

That could explain the .23 amp draw that goes away overnight. I will test that and check the 15 minute thing when I get a chance

[z28racergirl]

Did you ever figure this out? I had a CD stuck in my stock stereo and eventually it burned the motor out, and partially due to the RAP was draining my batteries. Mechanic finally figured it out for me, I know nothing about electrical.

Christine

[needbigtruck]

I looked for this thread because I had this happen to me again this past winter. I have not figured it out. I currently work at home and do not drive the truck every week. A few weeks back it was dead. I am now of the conclusion that my Scanguage, which is always plugged in, combined with cold weather somehow causes a small drain on the batteries. I have disconnected it and the truck has sat for 2 weeks (not all of it cold) and the batteries are just fine. It is probably never going to be solved. That's why they make battery chargers.

[ginger743]

I had an aftermarket alarm system in my car run the battery down after a few days.

I don't imagine you have an " aftermarket " alarm system in this vehicle but does it have an alarm system that's sitting there drawing current waiting for you to disarm it ?

Jerry

[needbigtruck]

I don't have any alarm system. Just the Scangauge, which will stay disconnected. I will never understand it but I'm pretty sure some relay is hanging up in the cold causing the small battery drain, and some how the Scangage has something to do with it. I would never have noticed until this situation of not driving the truck very often.

[DmaxMaverick]

Is it so difficult to accept the obvious? Scangage, or any diagnostic port plug-in, will draw power, key on or off. They work by opening the diagnostic channel in the PCM, and keep it open as long as it is plugged in. Diagnostic communication is continuous, but it doesn't come free. Bidirectional communication requires power. And, it isn't necessarily a "cold" thing. Cold weather starts require more battery power (for several reasons), so it is reasonable to see a condition that appears to be more pronounced during cold weather.