Battery is being drained overnight

[68_Step]

The 78 Chevy C-30 I just got is eating batteries. Something is draining them completely in a day. I have checked the obvious stuff, radio and all lights are turned off. Could an electrical short be killing the battery? The battery that came in it was dead Saturday morning, so I thought I may have left something on. I recharged the battery and Sunday morning it was dead again. I replaced it with a known good battery Sunday evening and tonight (MOnday evening) it is dead too.

How do I trace an electrical short? Will I need a multimeter? If so, will something I pick up at Radio Shack be ok? Any advice would be greatly appreciated. The truck is new to me so I do not have a past history of electrical problems...

[1985K10]

You can use a test light. With a good battery in the truck, disconnect the negative battery cable, clamp one end of the test light to the neg. battery terminal, and the other to the neg. battery cable. The light will be lit if somethings drawing power.Now all you have to do is pull fuses one by one untill the light goes out, then trace whats connected to the fuse you pulled that made the light go out, and you should find you're problem!

[SCOTI]

Tracing a short within the harness can be time consuming but here's some short cut's (pun intended). To start.... get the batt checked. Make sure the battery has all good cells (even if it's brand new). One bad cell & it can seem like a drain because no matter what, it won't hold a charge.

Put a ohm/multi-meter inline w/the battery (disconnect one of the cables & use the leads to complete the circuit). Start removing fuses from the fuse block one by one & look for changes in the meter. Any extra electrical stuff like pwr.windows or seats that don't work?, check them first because that's where you'll usually find shorts.

If everything appears well get the alternator checked & verify the diodes are functioning @ full capacity. There are 3 diodes in the alt & 2 can go bad so it will still show it's charging. Typically if/when the diodes go, they cause a short. Happy hunting.

[BeerMonkeY]

1985k10 is right ,but remember that some stuff is supposed to draw current all the time like the memory on the radio if its aftermarket. shorts are a pain in the a$$ to figure out.

[SanitysBane]

check out the voltage regulator on the alternator, thats were i would go first

[Prerunner1982]

i have had this same on going problem, except mine varied. for weeks at a time it would be fine, then for a few weeks, it would be dead after about 6-7hrs. i tried the whole pulling fuses thing and didnt find anything, i figured it was the alt. because it didnt seem to be working right all the time. i have recently changed the alt but havent left the battery connected over night to see..

[hotrodhomi]

does your truck have an amp for the stereo?

[68_Step]

hotrodhomi: Yes, it does have an amp behind the seat...

Tonight I will grab a test light and see it I can narrow it down. If that does not work I will pull the alt off and have it tested.

I have a set of roof mounted running lights that do not work, that will be the first thing I check.

Thanks!

[hotrodhomi]

The first thing I would do is hook up a ammeter in series with the neg, battery cable and see how much the current drain is. At first it will spike when things like your amp turn on but it should go down after a few seconds. then I would start by pulling the fuse out of your amp and if thats not it. I would then start on the fuse panel. If there is no change when you pull a fuse out, put the fuse back and pull another. Good Luck.

[SCOTI]

Another possible short I thought of is the horn. I swapped steering wheels on my beater a few yrs ago & then started having batt drainage probs. Turns out when I swapped wheels the horn kept going off so in haste I just unhooked it. It was still causing a ground fault I didn't consider & after 2-3 days of sitting it wouldn't start (overnight wasn't a prob).

[68_Step]

What I did: Charged battery, disconnected neg battery cable and hooked test light up between them neg battery terminal and neg battery cable, the light came on. I pulled each fuse, one by one, and the light never went out. There were two in-line fuses that I found, one for the amp and one for the radio, pulled them both. The light stayed on...

Does the test light detect a short, or a current draw ? If it detects a current draw and I unplug the radio (always draws power), should I leave the radio fuse out until I finish?

Going to check the horn...

Sigh, shorts suck!

[68_Step]

A bit of success: I was pulling one fuse at a time and was getting nowhere, so I pulled every fuse and flasher in sight, that made the test light go out! I used one fuse to cross the contacts on each of the fuses I found. I found two fuses that lit up the test light (1) tail lamps / courtsy, and (2) accessory fuse. Tomorrow night I will unplug the radio and amp and see if I can narrow it down to one of the two. At least I do not have to worry about the battery going dead tonight (hopefully). Besides a radio and an amp, anything in the truck that might draw power all the time?

Thanks for the help!

[NeCrOmAnCeR]

If you had the door open while pulling fuses, with lamps in the domelight/s it could be what was causing the draw on that circuit. Try it without the dome lamp bulbes installed

[Prerunner1982]

the clock if your truck has one will always be drawing, it may be causing the short and quick killing of the battery. as much of a PITA it would be you may remove the clock. mine doesnt work all the time either so i think that may also be my problem. i need to double check my door switch wires as i cut the in the past and they SHOULD be taped up, but who knows. i had the same problem of the light staying on when i removed all fuses, and in my case the door wouldnt be the problem as the switch isnt even connected. good luck let us know...

[68_Step]

I had the door open when I was pulling the fuses, guess that explains the "courtsey" circuit showing a draw!! I will remove the bulb tonight and see if that will let me narrow it down to one curcuit.

The good news: it is one of the two curcuits I identified lthe night before last. The battery is not draining now.

[68_Step]

I had the alt tested last night at O'Reily's, it is putting out 12 volts, they said it should put out about 13.5 to 14 volts and that 12 was enough to run the truck electrical system, but not enough to charge the battery. Is this correct? The alt is chrome, so I would like to keep it, can it be rebuilt?

[apstguy]

A car battary needs 14.4 volts to charge properly. 12 volts is too low. There are rebuild kits, but they are for factory alternators. You'll have to find the manufacturer to see if they have a rebuild kit.

[hotrodhomi]

If you find a shop that specializes in Starters/ alternators then they might be able to rebuild it for you.

[68_Step]

We do have a starter/alternator rebuild shop in town. I will go see them during lunch hour on Monday.

Thanks for the help!

[68_Step]

Sigh... I hate electrical problems

I took the alt to the local repair shop (O'Reilly's said it was bad) and the repair shop said the alt is putting out 14.2 volts and that the diodes are good. He did tell me one thing to check: He said if the wire that connects to the (my alt is a 3 wire) terminal marked #1 has power to it when the motor is not running, that will run the battery down. Will check that tonight.

Where do the 3 wires lead to? I have two wires that connect to a double spade treminal on the side of the alt. Those 2 terminals are marked #1 and #2. I have one wire that connects to a post on the back of the alt.

The two fuses that I removed earlier (tail lamps / courtsy and accessory fuse) are still removed; they were drawing power so I took them out to narrow things down.

Any ideas on what else to check? Before I set fire to it...

[hotrodhomi]

it sounds like it is in one of those two places. Do all off your lights work? if not, check those. did you ever try and pull the amps fuse?

[68_Step]

Originally Posted by hotrodhomi

it sounds like it is in one of those two places. Do all off your lights work? if not, check those. did you ever try and pull the amps fuse?

But those two fuses are pulled. Wouldn't that have stopped it, even though it was not really "fixed"? Yep, pulled the amp fuse...

[swervin ervin]

I've got a 87 Chevy van that kept doing this. It might not be overnight, but about every couple days it would be dead as a door nail. I tried everything I could think of to fix it. It come time for inspection and I knew the horn didn't work. After messing with the steering wheel to figure out how the PO screwed it up, I found out putting everything back right still didn't fix the horn. I went to Advance Auto Parts and bought a horn. Guess what, no more problems. This thing has been sitting for at least 2 months without being started. I just went out to start it and it fired right up.

Don't ask me exactly what I did to fix it, but it was something to do with the horn. I'm thinking the horn was on all the time, but with the horn itself being bad, I didn't know it.

[apstguy]

The horn relay was probably stuck on, so it kept powering the magnet in the relay. That could drain a battary overnight no problem.

[68_Step]

Originally Posted by 68_Step

Where do the 3 wires lead to? I have two wires that connect to a double spade treminal on the side of the alt. Those 2 terminals are marked #1 and #2. I have one wire that connects to a post on the back of the alt.

Any ideas where the three wires go? Thanks!