Toatally inept with electricity- need help!

smithy · Post by **smithy** » 04 Feb 2005, 09:14

I've got a battery drain issue that I must solve but I have a problem-I have very little confidence in my ability to troubleshoot an electrical problem. I need to test my fuse terminals for a draw on my battery with the ignition off, but I don't know what setting to put my multimeter on. If I can just locate the draw, I'm confident that I can fix the wiring part of it with not too much trouble.
My battery has been drained periodically but usually starts with a jump. Now it seems my battery doesn't even hold a charge! ARGH! I need to crank my car to test a used flow sensor that I just bought. The strange thing is, even with the old sensor my car would crank and run for 15-20 seconds. With the new one it won't start when I try to jump it. It will try to turn over and start to catch if I crank it long enough, but it just won't start. I do need spark plugs as well. As you can see, this problem has several layers, but I do need help with the multimeter so I can find the source of my battery woes! Pleas help!

Booch · Post by **Booch** » 07 Feb 2005, 17:25

Hey there I am an electrician by trade! How about that!
I am not so sure this is a battery drain issue so much as a bad battery issue. To verify something is actually draining the battery, you'll need to do a few things:
1.) Make sure your multimeter is fuse protected. If it is not, I don't reccomend using it. Radioshack and walmart sell them for ten dollars.
2.) Set your multimeter to DC AMPS (in the range of 0-10 or 0-100).
3.) Unhook the positive battery cable and pull it away from the positive terminal.
4.) touch the black lead to the positive terminal of the battery.
5.) touch the red lead to the positive cable.
6.) read multimeter to see if it deflects. If it does, you have a drain in the car's electrical system. If you try this and find a drain on the battery, email me at [email protected] and I will try to explain how to "shoot" the short circuit.

Post by **matthew1** » 07 Feb 2005, 18:53

If you guys do end up moving further on this issue, could you post your emails here in this thread? This is really good info.

Also, shouldn't there be a small drain when everything's off, to keep the clock running and ECU's memory loaded?

Thanks

egdeaile · Post by **egdeaile** » 07 Feb 2005, 20:06

Same freaking guy, went and got myself a username now. Anyways, sure I will be happy to post topics on here. I would expect the clock and radio to draw a maybe a combination of less than half and amp (and I think that is high. I know my own electrical system to be problem free, so when I re-install the battery, I will take a reading with my digital multimeter to figure out what normal drain is. Anything that is killing the battery will be VERY noticeable. Car batteries are pretty impressive as far as capacity, and if it is a short circuit draining the power out of it, there is going to be a significant amount of current coming out of it. I have tested it and 3 amps continuous for about 8 hours will drain my Interstate battery to where it will no longer start my car (don't ask, I was bored).
Again, hope that helps! Later taters!

-------------------
Christopher in Groton, CT
Proud owner of a '95 850 GLT and a 2000 V70 XC with combined miles over 280,000!

smithy · Post by **smithy** » 08 Feb 2005, 16:33

Thanks for oyu suggestion. I will definitely try it out. The reason that I am led to believe that it is something draining my battery is that it even happens with a new battery. The battery doesn't go dead overnight. In fact, if I drive the car every day, I don't have a problem. It happens when I leave it for a few days. This past time I left it for a solid week and I think it caused my battery's demise.

From what you said the draw with the ignition off could be very small and still cause the problem. From other posts I've gotten the impression that it could be anything from a bad ground to a short in a light bulb switch. I can't wait to find out what it is.

I have slight idea how to use my meter to measure voltage and resistance but do you think you could break down what each setting measures. Even just an example of what to use it for would be helpful. My meter has settings for AC V, DC V, DC MA and Ohms(in two scales). Thank you for your previous suggestion and I will try it as soon as I get a battery. Thanks.

egdeaile · Post by **egdeaile** » 08 Feb 2005, 17:19

Okay, with the problem carrying over to a new battery, I am definitely inclined to believe it is a short in the system somewhere. There are quite a few things that can cause this... anything from a damaged wire to a drop of oil on the wrong part of an electical connection.

"From what you said the draw with the ignition off could be very small and still cause the problem. From other posts I've gotten the impression that it could be anything from a bad ground to a short in a light bulb switch. I can't wait to find out what it is." --Yeah, you could be drawing as little has 1 amp and still having this problem. Yay for you... not really. This could get very lengthy and involved. I will do my best to instruct you on how to take care of this problem yourself.

First things first, under no circumstances think that the 12 volt electrical system in your car cannot hurt you. You can still get burns and "bites" from 12 volts. Never put any contact, live or dead in your mouth. You're just asking for it, because everything in the car is grounded to the body frame. This goes double for systems that no longer have their full integrity (i.e. short circuits).

"My meter has settings for AC V, DC V, DC MA and Ohms(in two scales)."

All right, as far as your meter goes:
AC V- Alternating Current Volts- Used for household stuff that comes out of the plugs. Almost completely useless in car applications. You would connect the black lead to ground, then the red lead to the "live" side and measure voltage. Unless you plan on rewiring your house, it's not much use at all.
DC V- Direct Current Voltage- Direct current is what comes out of batteries (and used by car systems). Any battery driven system used this, and this is what you will use for every voltage measurement you take in a car. To use this setting to troubleshoot, you really need to know what the meter is telling you, there are easier ways to do it.
DC MA- Direct Current MilliAmps- This will measure current in your car up to its fused rating (assuming it has a fuse). This is the setting you will need for performing the above mentioned proceedure. HOWEVER, I am not sure that this setting is large enough. I bought a FLUKE multimeter (very good, industry standard equipment). It is rated to 10 amps, and is very good for this kind of work. Radioshack sells a similar model for around 50 dollars, which also looked good. I highly reccomend getting a multimeter with this higher rating so you don't fry yours. They also make something called a "Clamp-on" ammeter (found 'em at sears), that can measure current through a wire merely by being clipped around it. VERY Handy device, and means you could just hook up your battery as normal and clip this around the positive battery cable without having to set up as previously described. It all depends on what you're willing to spend. Having the right tools is invaluable, however.
OHMS- this is for measuring circuit continuity. The lower the reading the more current will flow through it. A piece of wire should have a reading of 0 ohms (or close to it).

And, finally, how to freaking shoot a short.
This first proceedure will assume that it is an isolated piece of equipment that is causing the short (i.e. a switch or the winshield wiper motors or something like that).
1.) Set up the car as described before, with the positive battery terminal and the positive battery cable bridged by your multimeter. You may need to tape the leads to these things, because you will need your hands free for other things. Make sure your multimeter is indicating that there is current draw.
(OPTIONAL: disconnect radio and clock so that they are drawing no current from battery. This way, you can make sure that you get not false indications. If, with these disconnected, you measure no draw from the battery, then one of them is the problem.)
2.) Open your fuse box.
3.) Remove one fuse, and then check the multimeter. If the current draw drops or goes away, your short is in that system (or systems). I highly reccomend going in order and keeping careful track which fuses you have pulled.
4.) once you have it isolated to one system, problem spots are often times motors and switches. Check each one in that system. It may be time consuming, but it's better than paying someone else 100 (or more) dollars an hour to shoot your shorts.
5.) Let me know if you have any luck this way. If you find nothing at all this way, it means your problem is in wiring between battery and fusebox, OR in the alternator side of the battery (the more expensive to fix).

If you are near Groton, CT, let me know, I might be able to help you out. If you need something clarified, don't hesitate to ask, I'll get back to you probably the same day (I'm a message board addict).
Also, anyone who has questions can always talk to me on my instant messenger account "smlngpoet"

Post by **matthew1** » 08 Feb 2005, 18:32

Wow, great post Christopher, thanks.

Smithy, make sure it's not a light staying on. My trunk light switch is toast, so it doesn't turn off when I close the trunk. This cost me a battery. I would go out on a dark night, or turn off all lights in the garage, and look closely for lights that are on like that or say a door light. Always troubleshoot from easy to hard.

egdeaile · Post by **egdeaile** » 08 Feb 2005, 23:53

Thanks matt, just go stealing my thunder like that... actually, I hope it is a light, much easier to fix!
Oh yeah, something else about car batteries... NEVER TOUCH THE TERMINALS TOGETHER WITH ANYTHING. A voltmeter is okay, but shorting out your battery (touching something metal or conductive such as a wrench across the positive and negative terminals) is HIGHLY dangerous. As in, literally, big boom. Mostly on older batteries, but the new sealed ones can still do it. And in case you're wondering "so what?" You might not think losing your sight and being scarred for life is so cool after it happens.
Sorry, just something I had to rant about because there was a kid that just did this in my neighborhood.
Later!

Guest · Post by **Guest** » 09 Feb 2005, 06:11

Thank you for the wealth of great information. As soon as New Orleans gets back to normal after Mardi Gras I will get a new battery and begin hunting for the short. I can't wait!

smithy · Post by **smithy** » 07 Mar 2005, 06:27

Alright, I finally found my problem thanks in large part to the wonderful technical advice in this forum. I metered the draw on my battery when the car was off and narrowed the problem down to fuse terminal 15. It was about a 4-5 amp draw, more than enough to drain my battery. Since it was the fuse for all of the interior and courtesy lights as well as the door locks, I started looking for shorts in those areas. After about an hour I narrowed it down to the map light in my glove box. I replaced the face of my glove box a couple of years ago and for some reason it does not rest all the way back against the switch controlling the light. For now I just pulled the light bulb. My draw dropped to right around 1-1.5 amps. That should do it. I am going to keep my eye on it though, just to be sure.
Thanks again for your help edgeaile!