Hey Guys - Thanks for all your previous posts to help me with this project. I have a 68 firebird and I am trying to figure out if I have a draw in my electrical system. I have to charge my battery every time I let the car sit for a day or two. I am not sure if it's a bad battery or a draw in the system. The reason being that whenever I hook the battery up to the charger I have a relay that starts buzzing really loud but then eventually stops after a couple minutes of charging. It's the relay on the very inside of the front near the drivers side headlight (on the backside of course) opposite of the battery. Does this indicate a draw from a bad relay? Is this the horn relay? Thanks guys!

The horn relay is right under the voltage regulator. See: http://www.thefirstgensite.com/library/partscounter/illustrated/elect/elect2.html

The horn relay will buzz when the doors are open and the key is in the switch. (The reminder to not leave keys in the car.)

I would then use an ampmeter to check the level of current draw with the battery fully charged and everything off.

You are sure you have a good battery? You might check the voltage across the battery.

Take the battery out and charge it fully, check with a hydrometer, then get a battery load tester and see if it's up to snuff. Borrow, rent, or you can get one at harbour freight for 25 bucks.

Get a 12 volt test light, place it on the + post and the clamp for the + wire, if the light glows a little could be normal or u have a clock or late model radio in the car. If it lites up bright than there is a problem somewhere, u have to start pulling fuses to isolate the area with a problem. That's if u don't have a bad cell in the battery.

Charge battery, disconnect battery negative cable. Use a multimeter on the 10 amps scale (dc) connect negative cable of the the multimeter to battery negative terminal and multimeter positive to negative battery cable . Make sure everything is off and that the door are closed. The reading you get should not be greater than 0.050 amps. If greater do like coilster said and remove fuse 1 by 1 until reading is 0 or less than 0,050A. Hood light, trunk light glove compartement and alternator diodes are often the cause.

Thanks guys! I really appreciate the help. I will try this...I think I just have a bad battery but you never know. Thanks again.

Dont need to buy a load tester. The place you bought your battery should do it for free.

I had the same problem. New battery went bad.

I will be doing this soon since I have gotten tired of having to disconnect the negative terminal every night! I will test each circuit for parasitic draw by pulling each fuse one at a time to find the culprit. Once I find the fuse that causes the current to drop (ie, this is the problem circuit), then what do I do? What about the circuit causes it to draw a little current? I find the battery is usually dead in 24-36 hours. I bought a new battery last April.

If you haven’t already, you must have a good schematic for the car (try Vikki’s site) at this point. If you are killing a battery in ~24 hours, it should be obvious (like an amp or greater) (not milliamps) unless you also have a battery issue. Once the fuse is pulled and the current draw drops, you will know that the problem is downstream of that particular fuse. More than likely the problem is with one of the devices on that circuit and not some random short along the wire run. The notable exception is where a wire gets pinched usually because of something you did. So if this problem occurred shortly after something you did, look in that area for a pinched wire. If it was me, I would leave the fuse pulled and connect your ammeter in series with a fuse for later reinstallation into that fuse slot. This will involve some jumpers but it will prevent you from damaging your wiring or ammeter. Then it is simply a matter of disconnecting the end device, installing the ammeter/fuse combo and seeing if the current goes away. If the current goes away, the problem is on that load device or the termination near that device, etc.

BTW, if you get done with all the loads on that circuit and haven’t found the problem, then pick your favorite four letter word of choice because the problem is in one of the wire runs. And that my friend is where locating the problem gets real ugly. Let’s hope we don’t get to that point.

Instead of connecting the multimeter in series with the fuse, could I not just leave it connected in series with the negative post and negative cable (the way I had it when I was testing each fuse)?

Absolutely. Only drawback would be if there were multiple issues on more than one circuit. The other item to consider is where you are troubleshooting. If you are tugging on wires under the dash, you may want to have the meter in front of you rather than under the hood.

I would still fuse it unless your multimeter has an easily replaceable fuse.