phantom draw on battery

2002 ISUZU TROOPER

75,000 MILES

WARD

MEMBER
2 POSTS

Battery goes dead. Replaced battery and have trouble shot it as described below:

have connected a test light between the negative battery cable and battery and it light with nothing on (confirming there is a draw on battery). We then started pulling fuses one at a time. The only fuse that caused the test light to go out was the main 80A fuse confirming that the draw is on that circuit. Any idea what it could be?

Dec 23, 2011 at 10:48 PM

RASMATAZ

✓ASE Certified Mechanic
75,992 POSTS

You need to track that circuit down -try this don't remove the main fuse and disconnect the alternator-is the draw still there

Dec 23, 2011 at 10:58 PM

WARD

MEMBER
2 POSTS

now the light goes on momentarily and then off

Dec 23, 2011 at 11:34 PM

WRENCHTECH

✓ASE Certified Mechanic
20,761 POSTS

You can't use a test light to check this any more.

You will need a digital ammeter and a jumper wire with clips on the ends to do this.
First rig any door switches so you can have a door open without triggering the interior lights and unplug the hood light. Remove one battery cable and attach the meter in series between the battery cable and battery post. Take the jumper wire and also attach it the same way. Leave the jumper wire on for at least 10 minutes to expire all the automatic timers. Now remove the jumper wire and read the meter. Anything over 50ma is too much draw. The way you locate this is to start removing fuses one at a time until the meter drops to normal level. This will be the circuit with something staying on. Determine what components are part of that circuit and check them individually until the problem is isolated.

Dec 24, 2011 at 12:19 AM

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