can i use multimeter to find car short?

Determining if you have and finding are two different tasks. One simple thing you can do is put a light bulb in the path. If it glows, you've got leakage. If it doesn't glow, put the multimeter on the 10-amp scale across the light bulb and see what you measure.

Modern cars have all sorts of electronics that runs in the background. It's not at all clear what kind of transient current happens when you power it up. The lightbulb procedure protects your meter against these unforseen transients.

To find the "short" the easiest thing is to borrow a DC current probe and trace the wire that has the current. mike

Hi...

It surely won't harm your multimeter (used properly, of course), but on the other hand won't tell you much of interest either.

Today's cars use an awful lot of stuff that draws power continuously that you will find some current drawn even though all is fine.

Physically check the obvious stuff for starters. Trunk light, hood light, glove box light, for instance. Going off when closed? Young folks music stuff... power amp switching off?

Take care.

Ken

beerismygas wrote in news: snipped-for-privacy@k79g2000hse.googlegroups.com:

a short would blow a fuse.

Maybe your car battery is going bad. They only last about 4 years,less if you let them deep discharge.

In modern cars,it's normal for some current to be drawn even with the car not running,accessories and lights off.

it would HELP a lot if you said what make,model of auto,mods,options,the more info you give the better.

You can pull fuses one by one to isolate an excess current draw to one circuit.

A short will blow a fuse or burn a wire.

Intentionally trying to make a spark at your battery terminal is dangerous. Car batteries produce explosive hydrogen gas when charging, and a spark can cause the battery to explode - spraying you with acid and debris, possibly blinding you or severely burning your skin. Car battery explosions are rare, but not impossible. They DO happen and the result can be devastating.

You can track down a current drain by connecting your meter between the positive battery lead and the battery (with the car OFF) and removing fuses one at a time. If you try to start the car or use any high amperage circuits while doing this test - like the wipers, blower motor or rear defroster - you will likely blow your meter's fuse or damage or destroy your meter.

its a, (cough) 1985 ford escort. no electronics.

i will try this on the 10A meter setting to begin with and lower it till i get to the milliA.

The usual way is to connect the meter between the positive battery terminal and the positive lead after it is removed from the battery.

Bob AZ

i did that, but with the negativ lead as its easier to unscrew. the result should be the same.

You could also test your ground to see if it is causing poor recharging.. has happened to me before. Set multimeter to check for resistance.. put on lead on negative battery terminal and second lead on a ground.. preferrably the one your alternator grounds to.

My curent car, a 95 Lebaron, and my previous one, an 88 Lebaron, are supposed to be like this, but I can never tell the difference after the battery is reconnected. Seems to work the same.

If you are inclined to email me for some reason, remove NOPSAM :-)

My battery was dead if I didn't drive it every 16 or 24 hours, I forget which. So when I went away for Thanksgiving, I disconnected one side of the battery, and the battery was still able to start the car when I got back 3 1/2 days later. So I was using too much current when the car was off. (I already knew the battery was charging propertly.)

If using s light bulb to find a short, Pat Voss (the smartest car guy I know (via the radio)) recommended a #53, I believe it is. The guy has lots of meters, but I got the idea he thought a lightbulb was the easiest way. A 53 should be a bayonet mount, with the outer ground and one center contact, and a spherical glass not much bigger than a

I expect this will be in the self-service part of a consumer autoparts store, but there are so many new bulbs in the last 20 years that maybe not everywhere

It worked for me when I had an extra alarm accessory that ran all the time that was running down my battery. The bulb glowed then, but not after I removed the accessory. The clock in the radio is not enough to light a 53. Of course I already suspected the burglar alarm, and just didn't realize the beeper transmitter in that particular case used power all the time, not just when it waa alarming.

I see it was probably the belt. That's actually the first thing to check. EVen if they are not dirty, they stretch with age. Even if they are dirty, you can probably just tighten the belt.

Ihaven't read the rest of the thread, but I'm sure they told you about removing the battery from the circuit and using the ohmmeter part of the meter. You should make sure the voltage of the ohmeter is in the same direction as the car battery.

You didn't say what year or make or model of car. You should have. Late in the thread we find out that it has no powersteering. So it's not the typical car everyone was thinking of, but even if it were typical, you should give this kind of info.

If you are inclined to email me for some reason, remove NOPSAM :-)