The Stovebolt Site Forums The Shop Area The Electrical Bay key-off battery drain

OK guys, here's one from a newbee....I have a 56 Chev 3800 w/ 57 283ci. I'm loosing over 1/2 volt in battery overnight, with the key off. I'm an electrical idiot, so replaced battery, cables, regulator, ignition resistor, cleaned neg ground contact at firewall, and checked circuits by removing fuses, but still get a .4 volt draw when measuring between pos cable and battery. My auto shop said they could not find anything wrong with the alternator. Anybody have a solution to my problem, No, I don't want to sell the truck, I can beat this demon!! Winning suggestion wins a free trip to Sedro Wooly (just kidding). Thanks for any help...Frank

Alternators can and often do have internal shorts and still capable of charging the bat at 14volts. The typical alt tester won't indicate a problem. Using the same setup you used when pulling fuses, take the wires off the alt.

Had one on my 52,, never did find it,,I got me a disconnect switch, just turn it off when I am thru with it for the night,,,,,,,,,mine has a 235, with 12 volt,,,,,good luck .....Fred

you guys are fast...thanks for responding! I think the shut off switch is a good idea and was going to do that until I can find the real problem. Also, I'm not done exploring the possibility of the alternator. How do I check it? Remember, I'm an electrical idiot!! thanks, Frank

I am not sure,my brother spent about 2 hours trying to find me and he is good at this stuff, he also suspected the alt. as last result,did something with one of the wires on it, then the truck would not die after turning off the switch, he checked my electrical wipers, radio, was surprised that he could not find it, I told him to stop as he already spent a lot of time on it,, to began with it I replace a cable that was in bad shape,ground I believe it was, thought this was the problem, then I checked the alt... it was bad, so I bought a new one, thought this was the cure,, took about 5 days and the batter was so bad that it would not take a charge,,not to bore you anymore, if you find out what it is, I may go back and look again,, this has been about 2 yrs ago..Fred

A slight draw on the battery is normal if it does not run the battery down over a long period of time. There is slight drain from dust, moisture, or other foreign material in the switches & battery case. A battery will have lower voltage after setting awhile because the surface voltage drains off.

Let me try this again. Take the wires off the alt. If the bat stops draining down overnight, you can conclude there is a relationship.

I think the normal drain is less then 3MA..Fred

thanks everyone....I will try the alternator AGAIN ! This has more than normal battery drain, over .6 volts overnight, and will be dead in a few days....NOT ACCEPTABLE!!
....it is broke, and I've got to fix it or I can't "just drive em".......

frank, sounds like you're pretty capable, electrically speaking. If you find its not the alternator, and assuming you don't have a clock (or in internal one inside an aftermarket, modern type radio), alarm system or other obvious 'always hot' drain, check the cigarrette lighter and all light sockets and turn signal indicator for continuity that shouldn't be there (shorts) using a volt ohm meter (VOM).
tony

When I installed my new harness I had the same symptoms. I had wired my gas gauge to the wrong terminal on the ignition switch and the gauge was always on. Turn the key on and off while watching the gauge. Needle should jump with power.

Curt B.

Frank you might try this (I have heard people use it to find shorts). Take some type of device like a seat belt warning buzzer and hook it up between the battery and the positive cable. As long as the drain is happening it will "buzz". Now just go through your fuses and pull one at a time. As soon as the bussing stops you have identified the ciruit that the "drain" is coming from. I have never tried this but is sounds good to me. Good luck and keep us posted.

thanks for all your suggestions, I have tried them all (with some variations) switched gas guage (key activated), don't have radio, clock, or alarm, etc. But I may disconnect lighter to see if that is problem. Disconnect switch will be installed soon, until I find the problem...Frank

Frank do you have a ampmeter of some sort?

With the truck turned off just like you were going to leave it overnight. Disconnect the positive cable from the battery and measure the current flow. Start with a high range and then work down until you have an accurate measurement. That way you should be able to know exactly what you are loosing.

Then with the meter still connected, disconnect one electrical device at a time until one of them makes the current flow go away. That one is the problem.

Best to approach it with some sense of structure, perhaps pulling a fuse, and if nothing changes assume everything on that fuse is okay. Remember that some circuits are not fused on an old truck, and your problem may be something that doesn't have a fuse. To find those located each junction, like at the starter, and disconnect each wire while checking for the current flow to go away.

Before you buy and install a disconnect switch, have you tried disconnecting the battery overnight to see if that affects it? Could be a bad battery...

Where in the Seattle area are you? I'm in Kitsap county.

quick question - what engine? any aftermarket options? BIG question - does it have stock or HEI distributor? original or later steering column/ignition switch? original or later wiring?
when the engine is running, what is the voltage measured from the (+) battery post to frame ground?

hey hotrod.. stock 283 stock dist no options stock steering col and replaced ignition switch all stock wires. will check on voltage when running, but will loose .6 volts overnight.

could be some of the wiring insulation is breaking down allowing a partial short. will be difficult to find. Oldsub's suggestion of an ampmeter is a good one. moving wires with someone watching the meter you might get lucky. goodluck

.6 volts overnight.??? from what to what..??? are you sure its a current draw..sucking it down...its normal for a batter to go from being charged to stitting to loose a little voltage... but that doesnt mean its gonna loose .6 accumulative every day...like ten days loose 6 volts... is that whats happening..??? or just the .6 volts one night..??? and is ur voltage meter right..???