Heavy draw on my battery - Team Camaro Tech
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post #1 of 6 (permalink) Old Oct 17th, 07, 05:27 PM Thread Starter
 
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Heavy draw on my battery

Hi all, I have a 92 Camaro 5.0. I've been trying to sell it and dump the money into my 71 but been having some problems.

It seems like overnight after driving it less than a block, the battery was dead....DEAD< DEAD. So I charged it and within an hour it was dead again. I was hearing some type of humming coming from the throttle body area with the key off. I disconnected the positive and it quits. When I reconnect the positive, I hear a small clunk and the humming again. What would be causing this with the key off?

I checked the cruise control and it was in the "on" position. I turned it off and got the same symptoms. Any help would be appreciated.

Henry
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post #2 of 6 (permalink) Old Oct 17th, 07, 05:50 PM
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Re: Heavy draw on my battery

Get a test lamp. The most common type look like a screwdriver with a clear handle and a pointed bit and have a short piece of wire with an allegator clip on the end. You may have to engineer a way to connect it up since the bit don't bite and the aligator clip is likely too small to clip onto the post. A little enginuity will be needed.

Disconnect the negative cable, and insert the test lamp between the clamp and the battery post. Your electrical drain will illuminate the light but the current will be greatly reduced. Next, start pulling fuses, disconnecting devices, and separating connectors until the light goes out. Once you find the offending fuse, device, or connector, you should have narrowed the problem down and hopefully identified the root cause of the drain.

Be aware that the dome light will draw enough to illuminate the test lamp. Either close the doors or pull the dome light fuse as one of your first steps.

Heavy loads are often caused by shorted diodes in the alternator, so it's worthwhile to disconnect the alternator leads as one of your troubleshooting steps. Don't let the red wire touch ground though, since it's hooked straight to the battery source.

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post #3 of 6 (permalink) Old Oct 17th, 07, 05:53 PM
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Re: Heavy draw on my battery

are your cables new or corroded?
that clunk might be your starter?


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post #4 of 6 (permalink) Old Oct 18th, 07, 04:50 AM
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Re: Heavy draw on my battery

Quote:
Originally Posted by henval View Post
I was hearing some type of humming coming from the throttle body area with the key off. I disconnected the positive and it quits. When I reconnect the positive, I hear a small clunk and the humming again. What would be causing this with the key off? Henry
You've located the noise, now pull off the air intake and feel with the hand to locate further the source of the hum.

If it turns out to be the IAC (Idle Air Control), a stepper motor moving a pintle/needle in/out of an orifice in the throttle body to control engine rpm, the PCM may be at fault.

Pulling the fuse for the PCM/ECM and all being quiet may point to the PCM as the PCM controls the IAC. There is a separate fuse for input to PCM controlling other devices. By pulling this fuse and hum stops, I would suspect the driver inside the PCM may be shorted allowing current to pass through and to the stepper motor. Or, the injector(s), same power used to turn them on/off.

Kindda far fetch, but woth looking into to locate the humming source, feel it hum.

But as suggested by Dave, use the light and pull fuses also assists in troubleshooting. What you are hearing is the effect, you should find the cause.

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post #5 of 6 (permalink) Old Oct 18th, 07, 11:53 AM
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Re: Heavy draw on my battery

I had a pherd once that was draining my battery. If I let it sit for more than 24hrs, it would be too far gone to crank. After replacing the alternator and battery to no avail, I happend to walk by it one day and heard the fuel pump run. I popped the hood and discovered that the ingition, fuel injectors, IAC motor, fuel pump and every other electrical subsystem controlled by the ECM was turned on. The root cause was an ECM power relay that had stuck closed. The ECM commanded the relay off, but the contacts apparently were welded together. Hard to say if your system is similar or not without looking at a schematic.

Dave
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post #6 of 6 (permalink) Old Oct 18th, 07, 11:08 PM Thread Starter
 
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Re: Heavy draw on my battery

Thanks to all of you. Those are all great ideas and I'll give them a try this weekend. I'll post again to let you know what I find.

Thanks again, Henry.


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