Technical Current draw, dead battery

So now that I'm driving my car regularly, I'm having trouble with a dead battery every 3 or 4 days. I'm running a GM alt from a '88 Caprice. It's charging at about 13.2 to 13.6 volts. I did a draw test, where I pull 1 fuse at a time and check for a spark at the battery. Even tried several fuses removed at a time with the same result. The only thing I have directly to the battery is the air compressor, and that's on a switch that is on only when I drive it. I have the battery grounded to the block, and the block grounded to the chassis.

Anyone know what could be causing this?

Thanks. Art.

 

Might be you're not charging enough. Should be 14.2 volts just off idle. Put on some electrical accessories, to draw, and see if it stays at 14 volts, it should. Even with, say, hi beams, and heater blower on high.

 

Yep, you're just below the needed voltage. Every rod should have a battery shutoff too.

 

I did an air system for a friend of mine. He was having the same problem. He now pulls the huge fuse for the air ride system when he is through for the day..........problem solved.

 

It could be the alternator/regulator, but a dash clock will always draw current (but may do so only at regular intervals) as it never goes off with the key. Sometimes folks forget that fact. Unplug the clock (if it exists) before trying to find a problem with the wiring.

If I suspect another voltage drain, with the key off, I will usually pull the ground cable loose from the battery & put a tail light bulb in the circuit. You can put clips and wires on a bulb or use a commercial test light, or you can just have an assistant hold the bulb to the battery. Just use the right voltage bulb.

If it goes on at all or even glows, with the key off, there is a short or something's not shutting off at the switch/relay. (or it's the clock!) It is a dead short if the light is bright: that kind of short often blows fuses and melts wires. BUT a transient or "partial" short can make it glow weakly. It could be a fraying wire or even a full on dead short, but on a circuit with a bad ground, and thus yet it will glow weakly.

I will un-plug & re-plug everything one wire or plug at a time until the lamp dies. That will isolate the guilty circuit, but beware that bad grounds can "scramble" your expected results from the test. Check every ground you can identify.

 

Also, if you are using a relay for the compressor, that can definitely cause a current draw. When the pressure drops far enough to trip the pressure switch the relay goes live even though you have the main hot wire to the compressor switched off.


Edit: Your charging voltage is also too low. Check your regulator/alternator to find the cause.

 

There's a good chance you have a voltage drop in one of your battery cables


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Agree to the needed 14.2 volts.

 

low charging voltage AND a voltage drain tells me you have a bad diode in the alternator....change ALL of the diodes...they are usually mounted on a plate that can be removed/replaced easily.

 

Thanks for the replies.

I'm not running a clock, not even a radio with a clock. The battery cables are new and the terminals are clean. It is definitely not at 14.2 v. I will check diodes tomorrow. I didn't think of checking the relays or anything other than the compressor, in the air ride system.

Ulu, if fixing the alt, and the electrical in the air ride isn't the issue. I will try your "tail light bulb in the circuit" trick.

Thanks again, fellas. Art.