The situation:

3.0 amp draw after vehicle shut off (1997 F150; 4.6l; 4X4; auto)
New (rebuilt alt). Replaced unit that overcharged
New Starter
After starting, all gauges function normally, but after a few minutes, the oil and amp gauges go to zero.

Have pulled all fuses from underhood and dash boxes, but still have amp draw.

HELP!!!!! What next?????

Jim

 

A few thoughts:

- How are you measuring the 3.0 amp draw? For example, are you reading it with an externally-connected ammeter between the battery post and the battery cable?

The only "true" way to measure a draw is by using an external ammeter -- placing it in the path between one of the battery posts and the cable that attaches to that post. But you have to be VERY CAREFUL to do this only with the engine stopped and not cranking, or the current draw in those cases will just blow up your ammeter. The charging current from the alternator is often in the 50 A range, and the current when cranking is in the hundreds of amps.

- If you've pulled all the fuses, there are (should be) only a couple paths left: The starter, which is completely unfused (except by the battery cable itself, heh), and the charging cable from the alternator, which is fused with a "mega-fuse" (usually around 175 A) that's not pullable.

To see if it's the alternator charge path:

1. With the engine shut off, disconnect the cable from the negative battery post.

2. Disconnect the thick (usually red) cable from the binding post on the starter and tie its end in a location where it won't touch anything. Unplug the plastic connector from the alternator (usually three wires on it).

3. Reconnect the cable to the negative battery post. If there is still a draw, it's not coming from the alternator or the charging circuit.

Now to see if it's in the starter path:

4. Disconnect the negative battery cable again.

5. Disconnect the positive (red) cable from the starter, and tie it out of the way in a location where it won't touch anything (or wrap electrical tape around the end to insulate it). You definitely don't want that cable to be touching anything when you reconnect the battery in the next step.

6. Reconnect the negative battery cable and measure the draw, if any. If you're still getting a draw at this point, it would just about be having to come from somewhere in the wiring harness itself. (That's pretty unlikely, because a partial short circuit that would cause just a 3 A draw is very rare...and even in that case, such a leak would have to be ahead of the fuse boxes, since you've pulled all the fuses.)


Hope some of this is helpful; it's just where I would start if presented with that scenario.

 

Thanks; will give this a try.

Jim