Author Topic: '78 Chevy C20 Battery Drain  (Read 7650 times)

Offline alhrensblade

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'78 Chevy C20 Battery Drain
« on: March 06, 2006, 04:13:00 AM »
First off, I wanted to give a big THANK YOU to anyone that's helped me out over the past year- my C20 has gone from an ugly POS with one tire in the junkyard when I bought it, to just an ugly truck. First time I've gotten a vehicle running well from being almost trashed beyond repair. ^^

Anyway, I do have a question. I bought a brand new battery last March, as I had to borrow one from my other car to get it home. However, the past month, it's been going dead if not driven every 2-3 days (needed some clutch adjustment, and it was too cold, so I just didn't drive it.) I've taken the truck in and had the charging system tested, it checked out. I then grounded a test light on my dash, and checked the fuse block, finding the three fuses that are under load all the time, hazard, accessory, and exterior lights. I know I don't have a lighter socket, so that can't be a drain... my question is twofold.

1) What components actually use the 'Accessory' fuse? (Fuse I in  this diagram, the 'Chevrolet And GMC 1977 And 1980 C and K Model Fuse Blocks' section) I don't know what's connected to that, and it only had stock equipment on the interior.

2) Is it possible for something like a hazard switch or turn signals to 'halfway' bridge, and pass current back to the ground without actually clicking the light on? I've checked, and all my lights work as expected, so it's not a dead bulb/hazard issue or something.

I'd very much like to figure out where the battery drain is coming from, any help would be greatly appreciated.


Offline Lt.Del

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> '78 Chevy C20 Battery Drain
« Reply #1 on: March 06, 2006, 11:26:00 AM »
Are you sure your batter holds a charge?  It doesnt matter how old or new it is, it is not a deep cycle, so once you drain it just once or twice, you may ruin it. A deep cycle on the other hand is designed to drain and recharge, several hundred times.

I would recharge your batter using a charger.  Take it out and set it somewhere for a few days.  Test the voltage, should be 12.5 or so just sitting w/ no wires or chargers attached.  Keep the battery from any wires or anything--keep terminals clear of all wires.  Check the battery again the next day to take read of voltage.

It may not be your truck, it could be the battery not holding a charge.

Sgt Del

Offline alhrensblade

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Re: > '78 Chevy C20 Battery Drain
« Reply #2 on: March 06, 2006, 04:06:00 PM »
I'll do that- I've got to replace it anyway, the last time it died, it froze, and is now unchargable, according to the auto parts stores around here... but it is one more angle to look at, at least. Thanks ^^

Offline 79apache

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Re: > '78 Chevy C20 Battery Drain
« Reply #3 on: March 06, 2006, 06:01:00 PM »
Disconnect your neg. bat term. With key off, place terms of a tester between neg bat. term and a good ground. If you get a light or show voltage, you have a short. If so, pull fusesone at a time till you have no light or show no volts. That will be the circuit with the short.

If no light or volts, battery is suspect.
Good luck!

Offline alhrensblade

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Re: > '78 Chevy C20 Battery Drain
« Reply #4 on: March 12, 2006, 08:21:00 AM »
Thanks for the idea, 79Apache, but unfortunately, having done that, I'm faced with a slightly larger problem. The short, whatever it is, completely bypasses the fuse block- I had a bare block, everything switched off, all doors closed, hazards off, even had the taillights completely disconnected, and I still had a full 12v passing through the alternator. (On the plus side, I did discover my neg. cable needs to be replaced). But I'll have to crawl under, and see just how the short is happening, I can find nowhere under the hood or in the cab where it could be happening. My only theory is that somehow my positive cable's casing has worn thin enough/melted off enough to connect to ground somewhere. ><

Thanks again for the idea, though, I would've been going mad trying to track this down otherwise.

*goes off to buy fuses to replace the ones that shattered as they were removed*

Offline 123 pugsy

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Re: > '78 Chevy C20 Battery Drain
« Reply #5 on: March 12, 2006, 11:32:00 AM »
The alternator always has a live 12 volts -key on or off.Try this:Charge your battery fully.Disconnect the wire at the distributor so it wo'nt start.Turn the motor over a few times.If the charge in the battery is significantly lower than 12 volts,your battery is toast.I've had"84 month" batteries die after 10 months.BTW if your positive touches the ground you will get a nice fireworks show and not a slow drain.

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