Finding a Short

[Fergienewbee]

I have a short somewhere that drains my battery. I've been disconnecting my battery at night, but what a PITA. What kind of meter do I need to check for current? Where do I start?

Larry

 

[504]

What is the car,truck ,tractor?

 

[Don-Wi]

I think it's as simple as putting a light between the battery and the cable, then start pulling fuses one by one until it goes out.

Donovan from Wisconsin

 

[Heat Houser]

Use a volt meter. Disconnect the ground cable and place the meter leads between the cable and the battery post. Pull fuses and/or disconnect electrical equipment until the meter reads zero volts. Why is the problem always the last place you look? LOL

If you have electronics that hold memory using battery power, you will see some millivolt readings, you are looking for tenths of volts or more if it is draining your batt overnight.

 

[Ted in NE-OH]

If car or truck. See if glove comp light goes out. also look at trunk light, and hood light.

 

[Janicholson]

A volt meter or a milliamp meter will do. Both are found in a Typical meter. For old equipment an analog (needle type) meter is better because it is much less sensitive to variable voltage and spikes. The digital meter (unless expensive) will be displaying random numbers.
Process:
Charge the battery with it disconnected at the non grounded post.
Put the Volt meter between the battery post, and the disconnected battery terminal. (all things shut off)
If there is a draw, it will show up as a volt reading. Less than .5 volts will usually not be a substantial draw.
To find the issue draining the battery, just begin disconnecting things (reconnect each that causes no change)
I would start with the big terminal of the alternator (if it has one)
Jim

 

[Steve@Advance]

An incandescent test light will be your best choice. Volt meters are too sensitive, they will show minute insulation leakage that have virtually no drain on the battery.

Disconnect one battery cable, connect the test light between the battery post and the disconnected cable. If the light glows, there is a drain. Start disconnecting wiring until the light goes out.

If this is your tractor, common drain problems are water filled/corroded ignition and head light switches, and bad diodes in the alternator if so equipped.

 

[BhB]

If it is a GMC or Chevrolet truck the try taking the fuse out of the radio.
Bill

 

[Geo-TH,In]

Steve,
I know a person with an s10. After the truck sat
for 12 days battery was drained. It took a ma
meter to find the tiny mirror light that wouldn't
shut off.

I had a solenoid on seat belt release, car was 2
door, that wouldn't shut off. That took 4 days to
drain battery.

I installed new alternator on tractor. I checked
alternator for a drain, then wired both wires
going to alternator through the switch. I know a
few millamps will drain a tractor if it sets over
the winter.

So in my opinion, small drains are important too.

I remember when simpson 260 EVOM cost hundreds of
dollars. Today you can get good cheap EVOMs from
HF freight. I don't understant why people don't
have one. Sometimes HF even gives them away as a
gift. I have extra HF EVOM in every garage, pole
barn, house and carry one in truck. For under $20
HF freight sells a good digital amprobe that
measures peak current better than my old analog
meter. Great tool to have when measuring a
motor's starting current.

One time I had a lawn mower blowing a fuse. So
instead of buying fuses to test with, I took an
old round ammeter that came out of an old car,
installed wires with ends on it that I could slip
in fuse holder. Found the wire goind to
headlights had melted against the muffler.

So I like to use meters to test with.

 

[oldtanker]

(quoted from post at 19:59:59 10/11/14) I have a short somewhere that drains my battery. I've been disconnecting my battery at night, but what a PITA. What kind of meter do I need to check for current? Where do I start?

Larry

The best answers you have gotten is using a meter and start disconnecting things/pulling fuses. Basically you are isolating circuits to find the one with the problem.

Now you didn't state what the problem vehicle/equipment is. How long does it set between startups? Is the battery itself good? Modern cars and trucks pull millivolts when not running. If they set a considerable time the battery getting drawn down is a common problem.

Rick

 

[T in NE]

Set a digital volt meter for amps and see how much each circuit is pulling. 1/10 amp draw will kill batteries if they sit long enough. Had .17 amp kill 2 sets of batteries in the 4840 before we found it one winter.

Checking voltage only tells you if it's connected to ground. Which doesn't tell you much.

If you don't have a HF store around you can get a pretty nice one from walmart for about $25, the one I got has functions I rarely to never use but they were good to have when I needed them.

 

[Aaron Ford]

One of my friends had a battery running down and while I did show a drain, no fuse would cause it to go away. After a careful inspection of the wiring going to the fuse panel, I found a small wire leading out of the back of the switch. It led to a small box behind the grill. It was a CDMA GPS locating device installed by the last owner. Snip snip, problem solved. I think he sold it on ebay.

Aaron