Battery Drain - Checking The Circuits

[Pedro]

Shamelessly copied from a post by Mr. Linx (with thanks!).

Disconnect the battery and put an ammeter in series with it, then start pulling fuses until you get a current drop; that will identify the area where the discharge is occuring.
Make sure that you have the radio code if it has been coded though!

I'm presuming the ammeter is put in series on the positive side of the battery.

[HMK]

Yes, but remember to observe polarity.

Also, most of these cheap meters will only have a 'limited' current range, so DON'T operate any 'high current' devices (such as the electric windows - up to 20 amps) while the little meter is connected - or it will be a little 'DEAD' meter

[Pedro]

Hmmmm - so a proper -30 to +30 amp guage might be required?

The type you can fit into your car, I'm thinking.

[stevem]

Sorry,at a bit of a loss here. !!I thought an ammetre was for measuring the charge in a system,in other words is the alternator working !
Surely it should be a VOLT meter, and when fuses are pulled the reading should RISE, as no current is being drawn when the circuit is isolated that has the current draw !!?

[melinx]

A 30 amp meter wouldn't be sensitive enough to to show the sort of currents that will flatten the battery in a few days; an 'el cheapo' digital meter on the 1 Amp range is ok, but as HMK says, don't switch on any heavy current devices while it is in circuit and take the bulb out of the interior light while you have the door open pulling fuses, since that will draw a considerable amount of that 1 Amp.
To answer your earlier question : - it really doesn't matter which terminal you disconnect and even if you connect the 'el cheapo' meter the wrong way round, the meter will show a minus sign but the reading will still be correct.
To answer stevem : - An Ammeter measures the current flowing in a circuit ( both into and out of the battery )
The change in voltage would be far too small to detect since you are dealing with a battery that will supply hundreds of Amps to the starter and still maintain 12 volts.