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I have a constant battery drain on my 56 Chevy P/U. 12v system. How can I run this down? Can I find the drain without unhooking EVERY item one at a time to see which one stops the drain?

Timmer,

Have you discounted the battery as the source of the problem itself? Any device that is switched won't drain on the switched side if the switch isn't switched??? This sounds goofy, but If you read it a few times it might make sense.

This leaves everything on the batt side of the system. The problem could be a high impedance ground..a short that is going to ground, but not direct enough to make smoke or blow a fuse. Look at obvious places, places where wires run near points that might chafe or rub.

The taillights are switched, but the brake lights aren't. The headlights, dash light and dome light are all switched. A alternator can back feed, but I don't know about a generator.

If the battery is charged, the truck sits for 3 days without being driven, and the battery is now half discharged, it is a drain in a un-switched circuit.

Make sure it isn't the battery...pull and twist the wiring harness as you look for wear spots, and just generally poke around. If nothing develops, then do the "remove-a-fuse" drill.

Stuart

Timmer,
A real quick way to determine if you have a short is to turn all switches off (key, headlight, door, etc.); disconnect the negative battery terminal; touch the negative terminal to the negative post, if there is a spark, you have an short somewhere. A good suspect is a hanging brake light switch.
Good luck.

Pull the fan belt off, if the generator turns, your regulator is bad.

Do you have an ammeter? Does it point to negative all the time?

If you don't get a spark as 1212 suggests then you can hook an ammeter between negative and cable and check for a load. But only if you don't get a spark, or your ammeter can read a minimum of 10 amps. Otherwise you might pop the meter's fuse.

I had one about 2 yrs ago,never did find the problem so I installed a quick dis-connect switch....best of luck,,,Fred

Usually the way you find these things is at the fuse box. Pop every fuse out one at a time, and check if the battery drain stops. Once you know what circuit is draining the battery, you can eliminate it by disconnecting each device on the circuit one by one checking the battery drain as you go.

You can use a test light in some situations for battery drain, but it won't necessarily light up with small current losses. It is better to have a voltmeter across the battery terminals to check it.

For small current drains, disconnect a battery cable and then put a resistor (anything bigger than 1,000 ohms will work) between the battery terminal and the disconnected battery cable. If there is ANY voltage across the two resistor terminals, there is a current drain on the battery. Keep looking for current drains until the voltage across the resistor is zero.

Don't try to use the current function of the ohmmeter, because you will usually burn it out. The method I outlined above will protect your ohmmeter from excessive current.

Timmer,

A bunch of great tips in the search for the gremlin, but don't forget, it probably isn't a "device" that is shorting, but rather the wires running to it. You can also take a flashlight and look around under the dashboard. If the leak is there, you should be able to see a small pile of "amps" on the floor that have fallen out of the broken wire..look closely as they are mighty small!

Stuart

Thanks guys, lots of great tips to work on over the weekend.
I already have a battery disconnect, just to keep me from having to jump it off.
BUT, I want to find that sucker.
You know, this is the kind of stuff that starts a frame off restoration. Heaven forbid!

My 77 Corvette had one of these nightmare drains. Turned out to be a short inside the starter - not the solenoid, it was actually somewhere in the starter coils.

My drain started when I installed an alternator. I haven't yet had time to trace it but that's where I'll start. For now, I disconnect the battery if the truck will sit for more than 3 days straigt.

Unfortunately I am facing a similar problem. Just switched to 12 volt and am using a 12 v generator. I switched the headlight switch, resistor in the fuel guage side and that's about it! Darnit. The guage says charging when I'm running her but darn if the batter isn't drained after a couple trips down the road. I hate having to park on a hill!!! Any ideas appreciated. Also, someone assure me it is infact OK to use the voltage regulator from my orig. 6 volt system with no mod. right? tia.

TT,

Generators...HRL territory! I truly don't know squat about generators, but I would be highly suspicious of using a regulator designated for six volts with a updated system putting out 12 volts. The regulator is just a voltage sensing switch..I think if it were adjusted to "switch" properly to control a 6v system, it wouldn't accurately control a 12v system.

The very least I would do is take a battery voltage measurement with truck at rest, and another with the engine running at whatever RPM would equate to charge. You will want to see a marked difference. Everything might be working properly, just not "enough" properly.


Stuart

I hear yah. The articles I read made no mention of the voltage regulator as an item needing attention..however what say makes sense. Maybe the regulator can be adjusted? Hate to lose it...it's an orig. part. I've looked around and have found NOS 12v generator compatible voltage regulators (Delco Remy) 40amp that look dead on the same as what I've got...3 tabs etc. Is that what I need?

I hope I don't lead you down the wrong path but when I put a new regulator on the 38 the fellow I bought it from adjusted the voltage it puts out to just over 8 volts max. I am NOT an electrics expert but from what he said it would not be surprising to me if the only difference in 6V & 12V regulators is the adjustment. This guy rebuilds starters, generators, etc. so he should know what he's talking about.

Be sure to have your battery tested for a bad cell first. This is the time of year they really like to go bad. I lost the battery in my 48 this year after 8 years of service due to a really cold spell we had.
Scott

*Doh! Maybe I have the answer...maybe. I never did polarize the gen. after installing the new 12 v version....heading for the garage now. Oh the shame of it all..if that is the problem.
**Doh update. I polarized the gen. and that caused the battery to drain fast! Put the charger on the battery and get a nice disturbing hum from the generator. What the heck is going on? I've disconnected arm and field to the voltage regulator so I can safely charge the battery. BTW - yes, the voltage reg. wires to field and arm are going to the correct spots...can't miss the big "f" stamped into the generator...that is an "f" isn't it??? On drivers side.

Sounds as though the regulator points are welded closed. When the generator is not charging, the battery should be disconnected from the generator by the regulator.

Ouch. Thought I smelled something. What would cause that? Is the 12 v. generator going to be ok? Was this caused by not having a 12 v voltage regulator? When I polarized the gen...could that have caused a problem??

OK, all you guys are too darn nice. Not one of you sad what a fat head I was. Good group, patient too.

I failed to read the details!!! I never installed a 12 v. voltage regulator and basically that was the problem. To boot, I had a really dodgy ground strap from starter to frame. So I put in a nice shiny ground strap, new 12 v voltage regulator and it fired up in a completely new way She's charging great, lights are blazing and life is good.

SHEESH, next time don't be so nice.

glad that you found the problem............Fred