Use of clamp on dc ammeter

Thanks for the help, guys. It seems to be working now.

I tried it again, put the clamps around the negative wire from the battery ( it was easiest to reach), turned the meter to DC Amps 0-40, and it started giving out random numbers. I zeroed it, as suggested, and it started to read out the draw.

I believe the culprit is the car radio, which we saw going on and off by itself while the car was parked the other night. This AM, we had a dead battery (almost new battery, by the way). I measured the amp draw with the radio fuse pulled, and it was very minimal. When I put the fuse back in, with the radio off, it was pulling about 1 1/2 amps, which I think would account for the dead battery. I think I need a new radio!

Thanks very much. I knew you guys would come through!

If it works with detecting the lights - and turning off everything (but the phantom) results in a meter reading of 0 amps, then you can be certain it will detect a few amps current. At that stage, I stop using the clamp on and pull the battery cable - then use the meter leads on a 10A scale - with the leads connected between the battery and the removed cable.

That will easily detect low current draws. Just be sure you don't inadvertently turn on something or try to start the vehicle, which will blow the meter due to current overload.
(I don't recall if the Sears meter has direct current detection with the leads - but many meters do).

Phantom draw will be very low, probably <50mA range or lower. Then after the car sits "idle" for awhile (no activity through the computer for 10- 30 min) it will be even go lower than that. I'm not sure you will be able to see such small ranges on that meter.

Be sure to zero the meter with the jaws closed, and not around a wire. Then try the lowest range 0-20A to see if it can detect that small current. Clamp on meters don't do well when there isn't much magnetic field built up around a conductor unless they have an external sample loop.

Yes, try the experiment suggested by Drycamper11 to see if the meter will indicate a higher current. Headlights should be fine at the 0-20A scale.

Orcadrvr wrote:
I put it around only one wire, but no change.

With it on the positive or negative battery cable, turn on the headlights, parking lights and radio and see what you get there. If you are using it correctly, it should show a large draw. Once you know it's working, start turning things off.

Hit the zero button on 0 to 40 . It's got to be around a hot lead I believe maybe to small to measure.

I put it around only one wire, but no change.

Did you put the clamp around a single wire? Can't put it around multiple wires or cables.