Randy82WS7

how do you guys go about checking for a small battery draw by checking it between a battery cable and battery post ?

test light ? or is a small draw even enough current to light up a test light bulb ?

if i were to use a digital multimeter then what setting should i use ?

im thinking it may be the sterio i installed recentl,y but who knows, it may be glovebox light or trunk light or something else('84 impala)

never had this problem until recently after i cut the cumputer out(so that i could swap a non CCC carb on)
and put in a cassette sterio

i dont know if i need to look for amps or volts in the draw between cable and post




thanks for anything

Vader

Typically, an ammeter is used in series. Disconnect a battery cable, connect in the ammeter to complete the circuit (noting polarity), and read the current. Start with the meter on the highest current scale just to be safe, then lower the scale as necessary for best resolution.

Randy82WS7

what setting would this be on a digital multimeter tester ?

theres ohms(resistance) and volts and continuity, i dont see anything else, no way to measure amperage flow with a multimeter afaik ?


thanks

Ice Fisherman

If your meter won't measure current, you'll have to use something else.

firebirdjosh

iTrader: (1)

You'll have to get a better meter then.

Forshock 85TA

harbor freight sells the little yellows ones for less than $5. we own 8

shawnc16

Any meter will work fine as long as it actually reads amperes. Put the meter on its highest setting so you dont blow the fuse!

2kflhr

iTrader: (1)

Most meters do not read current without an amp clamp adapter, only voltage.

Take a volt-ohm meter and connect one lead to the negative battery post and one to the ground cable. Note if there is a volt draw. If no voltage, no short or nothing is drawing voltage. Keep in mind that minor things like the radio may draw minute amounts of current for the pre-set memory. Your system is only 12 volts so that setting if selectable is fine.

firebirdjosh

iTrader: (1)

Either: 1. your method won't help at all for the reason you mentioned, or 2. you have your terms mixed up.

PhLaXuS

You can put a giant resistor in-line with the battery + terminal and measure the voltage drop across it. The only problem with this setup (and all 12VDC in-car current measurements) is that even with eveything off, if you're getting a load anough to actually notice, it's probably going to be in the 30+W range. Resistors that large can be expensive. Not necessarily are, but can be.

NEEDAZ

I don't even know where to start with this one, but just ignore it.
And if using a resistor as a shunt you would need a vary low value/high wattage PRECISION resistor (and an accurate mV meter), or just get one sold as a shunt.
But it would be cheaper to just buy a DMM that will read current directly. And YES they are easy to find without clamp-ons.

2kflhr

iTrader: (1)

Ok, Ignore my previous post. But if I remember correctly you can connect a 12v test light between the negative post and negative cable and if the light glows something is pulling current. Is this not correct and will a Volt-Ohm meter not work the same way?

firebirdjosh

iTrader: (1)

Bulb will work. Volt meter will not. But glowing doesn't mean anything unless you know how much you are drawing and if its within acceptable range. That's like measure clearances with a yardstick.

flrtin1

Since this seems to be a question asked often and since this was way to much info to type and explain it in a way people would understand I dug out my books (I am retired so don't need to have my books handy anymore ) This info is a little dated (1990 or so) but the basics never change....lets see if this works

Edit: lol excuse any underlining or notes this was a book I used in my GM electronics certification class

NEEDAZ

I get where you’re coming from now. The thing is a test light and DMM (set to voltage) act like two different thing. With the DMM set to voltage it should be ‘seen’ as an open (should be at least 10Mohms per volt), so no current flow. With no current flow you get no voltage drop. So using the voltage meter like this should show you the full battery voltage as there is no voltage drop through the circuit. With the test light, you have a relatively low resistance so you can get current flow, and then voltage drop across the filament, depending on the resistance of the rest of the circuit.
I don’t like the test light method because it assumes too much. The amount of current to get the light to light up will depend on the light bulb. Different light bulbs will light different amounts for the same current. Way to hit-and-miss. I like the post above (other then the test light part).
Get a DMM that will read current and go at it.