Please help with a weird electrical problem.

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Oct 13, 2007 | 02:22 PM

Bagel Maker

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4th Gear

Joined: Sep 2007

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Please help with a weird electrical problem.

Hi there. This is my first post. I have 71 Vette, 350/270, 4 speed, air, and unmodified. It has been sitting in my garage and not started for about four months so the battery was dead (clock I guess). I put the charger on it this morning for three hours. Here is the weird part. When I got in to start it, there was a strange harmonic hum in the radio as I turned the key on. It hummed about 1 second then stopped. I turned the key off. Each time I turned the key on, the hum would come from the speakers then stop. Then I tried to start the car and got a loud buzzing noise that seemed to be coming from above the passenger foot well or just to the right of the center instrument cluster. Each time I tried to crank it, I got the buzz and it would stay as long as I held the key in the start position. The car would not start as the starter never turned. I was worried about damaging the electrical system so I disconnected the charger, tried it (starting) again just to see what would happen but the system was totally dead as if the battery was disconnected. I haven't put the charger back on for fear of screwing up something or starting a fire.

Do any of you guys have any idea what the problem might be because I am not an electrical guy and I am completely dumb founded. Thanks in advance.

Oct 13, 2007 | 02:54 PM

bj1k

Le Mans Master

Joined: May 2006

Posts: 5,814

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From: Pittsburgh suburbs Pa.

Check grounds first.

Quote:

Originally Posted by Bagel Maker

Any time you have a weird electrical problem always check your grounds first, especially your battery ground. ( clean and tighten it ) Bad grounds can cause all kinds of goofy problems. It sounds like your noise is coming from the starter area since it is behind your passenger foot area. Thats where your starter is. Clean all of your starter connections first and go from there. In the mean time I would disconnect your battery and charge it overnight.

Oct 13, 2007 | 07:59 PM

longbros

Burning Brakes

Joined: Feb 2004

Posts: 924

Likes: 2

From: Kearneysville West Virginia

If the battery has been dead for that long, you need to put it on charge for much longer than three hours before trying to start it. Sometimes, when batteries are dead for a long time, they will not come back. But, most times they will, but the process starts off very slow. Let the battery charge for a day before you try and start it. If you have an ammeter on your charger, you might notice that the charger appears to not be charging at first. This is because the battery starts out taking in very little current, milliamps. After a while, if the battery is going to come back, the charging current will slowly increase, and show some amps, maybe 5-10 amps.

The buzz you heard was the 60 hertz or possibly 120 hertz from the battery charger. The battery was completely dead, so it was transparent. All your car was seeing at the time was the output of the charger, which is not all clean DC like would come from a battery. The output from the charger is unfiltered rectified AC, which depending on the rectifier used by the charger, will produce 60 or 120 hertz noise on top of the DC charging voltage.

So, first, let the battery charge a day before you try to start it again. If the battery does not come back, it is time for a new battery. I hope this helps.

Oct 13, 2007 | 08:11 PM

xCCTer

CF JASOC Member

Joined: Feb 2006

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From: Downtown Annapolis, MD. The Future is where we all have to live. Let's not screw it up.

St. Jude Donor '08-'09-'10-'11

The thing that sounds most peculiar is that your clock works.