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Electrical leak

I have a 1996 C1500 pickup with a 350 V8 and automatic transmission. I seem to have an electrical leak. When I put a VOM in-line with the battery and have everything turned off the meter still reads 0.89 amps. Not enough to be a dead short but enough to cause the battery to go dead in about two days. How can I isolate the short/leak so that I can determine what needs fixing? Any and all suggestions will be appreciated.

Before you take any kind of voltage/amp parisitic draw tests from the battery, let the vehicle sit idle for an hour before performing these tests. There are some modules that can draw volts/amps for a period of time before they go to sleep.

Tester

umm a dead short will SMOKE a fuse.

maybe you were taught different (BUT WRONG)!

its called DARK VOLTAGE.(DRAW.PARASITIC LOAD).not a short!

good shop is your best bet.

good luck

If the amperage is still too high when measured after the car sits, start pulling fuses until it drops. You can check the VOM or put a light bulb in line instead. when the bulb dims, you found the circuit at fault.

Hood light?

Since you had the hood open to do the test, the hood light was probably on, and drawing just shy of an amp.

Alternatives: plug in devices (radar detector, cell phone charger, ipod charger, etc).

If not those, I need to think about it. I have a 97 Chevy C2500, so I could check the dark current.

gerG

Also, be sure your ammeter is calibrated and zeros out

Thanks for all the replies. I’ve disconnected the under-hood light so it is not drawing any current. I don’t have any plug-in devices plugged in. I suspect the clock and other devices will draw some current (perhaps in the milliamp (sp) range) all the time. When I connect the VOM, closing the circuit after it’s been disconnected for some time, is there an initial period when some devices will draw a higher current before they ‘go to sleep’? I have tried pulling the fuses one at a time (leaving the interior light fuse pulled as the door has to be open) but have not seen a significant drop in the current draw as I pull the others one at a time. Are there devices that are on all the time and are not fused (exhaust gas analyzers or air bags for example)? It doesn’t seem like that should be the case but I don’t know that it isn’t. And, the VOM is digital and doesn’t require calibration. It is an auto-ranger type. So, any other suggestions would be welcome. I’m stumped. Thanks again.

I am not sure what the normal current draw is for your vehicle but typical vehicle current draw runs around 25-30 milliamps. It does sound like something is drawing some extra current. If you have pulled all the fuses in the dash and under the hood and still haven’t seen a drop in current drain then it appears the load isn’t tied to the fuses. Is there any add-on device hooked to the battery? Try removing the rear connection to the alternator and see if that makes any change.

Yes, you need to wait about an hour after completing the circuit before considering the current draw to be too high. Your door needs to be closed. Having it open may keep something awake. Anytime you pull or put fuses back in, it may wake stuff back up, so you’ll have to wait again. I suspect that the normal drain should be less than 50 mA (0.05 A).

Thanks again for all the replies. I have tried disconnecting the alternator and even had it checked. It passed all tests. Today I will attach the VOM and wait for at least an hour before attempting anything else. Then I will pull the fuses one at a time until they are all out or I see a significant change in the VOM reading. Thanks again. Fingers are corssed.

Sorry to hear about your fingers. Here is an article which may give you an idea, or two: http://www.aa1car.com/library/battery_runs_down.htm
Also, if something comes alive (uncommanded), it can die again, and if you’re not there, you won’t know it. It could be something which is a big drain, which comes on for a few minuets, then, cuts off…and, again. One component that comes to mind is the radiator cooling fan, turned on by a malfunctioning fan relay. I’ve seen it.
An hour, or two, or four, after the car is shut off, sneak up on your car, and look and listen for any light on, or elecric component on. If you note one, that could be your, “AHAH!” moment.

Thanks for the pointer to the article. Very helpful. But…messing with the fuses and relays must have cleaned a contact or unstuck a stuck relay. The problem seems to have gone away. It may be worth reporting though that after connecting the meter in line between the battery terminal and the cable the last time, the initial draw was 0.89 amps then after about 30 seconds it started dropping: 0.89 – 0.69 – 0.22 and came to rest at 0.01 amps or 10 milliamps. After watching it for a while it stayed at 0.01 amps. Then, checking the battery every 12 hours or so there was no significant drop in voltage. I’m still stumped, but will have to wait until the problem recurs. Thanks again to all the posters who offered suggestions.

Hope you all had a nice Thanksgiving.

Barry

Do you have lighted (vanity) sunvisors? They are notorious for not turning off and will pull almost 1 amp when on.You will have to unplug them to test (the ones that are always on do show a degree of being melted)

Hi Barry.

Do you by chance have an aftermarket stereo system in the truck? I had an amplifier that would do this same trick.

I checked the current on my '97 C2500. It dropped below .1 amp after the inside light went out. I didn’t notice any tapering off, but I wasn’t really looking for it at the time. Did the current drop in steps on your truck, or was it a gradual fade?

gerG

That last slow drop in amperage, from 0.89A to 0.1A may have been the capacitor(s) charging (as reserve power) for the air bag system.

No, no aftermarket anything. Everything’s stock and original except for normal maintenance stuff like plugs, belt, hoses, etc. Oh, the intake manifold gasket had to be replaced because it was eaten by the Dexcool coolant. And there was a new alternator. But all else is just like Detroit assembled it. 84K miles ago.

The drop in amperage was in steps. I’m not sure I caught them all. There may have been one more. The steps may also have been a function of the meter if it’s doing any kind of sampling…but that sounds too sophisticated for my meter. A Micronta (RadioShack) DMM that I got about 20 years ago. ‘Lab Standard’ they called it. hellokit’s remark about airbag capacitors sounds right. But since I had left the hood open I didn’t have to open/close the door causing any interior light time-out.

Thanks again.

Barry