Electrical problem
1988 Acura Legend 6 cyl 242k miles
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Hi Guys,
Something is slowly sucking power from my battery while the car is off. If I don't start it for about 3 or 4 days, the battery is so dead that I can't even pop the trunk.

Key Notes:
1. The battery is brand new.
2. No visible lights are on anywhere.
3. My cable terminals are loose and I tighten them by wedging screws between them and the battery terminals.

I have 2 questions...
1. How do I use a voltage meter to find the source of the power drain?
2. Can the inserted terminal screws have anythng to do with the problem?

Thanks,

Paul.

Get a test light and disconnect the negative battery cable now put the light between the cable and battery negative post is the light On? If so start removing fuses one at a time -the fuse that turns off the light is the trouble circuit. Then break out the electrical wiring diagram.

In the event you removed all the fuses and the light is still On disconnect the alternator batt. feed and the connector-if this one turns off the light-the alternator has bad diodes.

Or you can use an ammeter which is the preffered method to check for an excessive parastic drain

Thanks Ras,
I have one of those 'multi-meter' voltage meters. I set it to 50V and when I test the batt with the car off it reads between 12 & 13, which (I think) is good. But when I disconnect the -ve cable and put the VMeter between the cable and the -ve post it reads nothing. Actually it jumps backward below zero.

I put the VMeter on lower settings (like 10V or 2.5V), but still nothing. I even tried disconnecting the +ve cable (after reconnecting the -ve cable of course) and running the meter between the +ve cable and the +ve post, but still nothing.

What do you think?

Paul.

Disconnect the negative battery cable-put the VM on 50v scale-Now put VM black lead to the Neg. battery post and Red lead to the Neg.cable if you have battery voltage start removing fuses as stated earlier.

Thanks Ras,

The VM worked this time. But I pulled out every fuse, even the big ones that were screwed in, and disconnected the alternator and nothing made it drop to zero.

However, when I pulled out the big 70A "Battery" fuse the VM dropped from about 12.5 to about 11, does that mean anything?

If not, what would you recommend I try next?

And I forgot to say earlier that the alternator is about a year old.

Thanks,

Paul.

Disconnect the alternator connector and battery wire from it-do you still have battery voltage? Let me know.

Yeah, I disconnected the only two wires coming into the alternator. There was a small one on the side (near the top) that lead to the battery, and a combo plug at the back which lead to a large electronic cluster. Then I checked the battery voltage again and it was still about 12.5.

Also, just in case there was something up with the neg battery cable I also grounded the +ve pin of the VM on the engine block instead of the -ve terminal while checking voltage and that didn't change the reading.

What about the 70A fuse that made the reading drop from 12.5 to 11, is that significant?

Thanks again,

Paul.

But when I disconnect the -ve cable and put the VMeter between the cable and the -ve post it reads nothing. Okay try starting the vehicle and check the battery voltage you should atleast have 13.5 volts while engine is running

Ok Ras,

I started the car and checked the battery with the neg cable attached and also detached. The VM read 14 with the cable attached and 13 with it detached.

Then with the car still running (just for fun) I hooked the VM between the -ve battery post and the -ve cable (as you described in an earlier post) and the VM read zero. And remember when I do that with the car off, it reads between 12 and 13.

What do you think that means?

Paul.

You're good to go-14volts for me running your alternator is doing its job-so whay is it doing now. Maybe you might consider another battery.