94_Bama

My 94 pu has been having some battery issues (constantly being dead). I got it checked out and was told my AM1 40 fuse circuit is causing the drain on the battery. Well i havent had the time to check it out due to working but i have jumped my truck off here and there and it has been fine once its running, but the other day i was driving down the road about 20 minutes or so after the jump and the truck started to sputter and then shut off. I got it to the side of the road and tried to turn the key over but nothing came on (battery dead). Now my question, could this drain cause my truck to die going down the road? Bad altinator? or could this be a completly different issue?

RJR

Your truck runs on gasoline, but all of the engine control systems need electricity. So, yes, if the alternator isn't charging and the battery gets too low, the engine will shut down. Just jumping the battery to get the engine started doesn't charge it up, so you can only last a few days operating that way.

The AM1 40 fuse itself probably isn't draining the battery. However, from the wiring diagram it does appear to be involved in the proper operation of the alternator and voltage regulator, and if it's blown your alternator likely isn't working. Without the alternator charging your battery, other loads have run down the battery until finally now it doesn't have enough charge left to run the ECU, fuel injectors, ignition, etc., and your engine has stopped.

You need to find and fix that fuse. Hopefully that's all that's wrong, but usually a fuse blows because something else is wrong, so don't be too surprised if it blows again right away, in which case you'll have to dig deeper.

Perhaps you could go back to the folks who checked it out and ask them a bit more about what they think the problem is, and how they suggest fixing it. Seems kind of superficial for them to just tell you "the AM1 40 fuse circuit is draining your battery" and not provide any direction as to a solution.

I need to correct my post above. After looking at a more detailed wiring diagram, it's pretty clear that the engine wouldn't run at all if the AM1 40 fuse were blown, because it runs the ECU and ignition among other things, so that's likely not the problem. What I'm guessing the mechanic told you is that something on that circuit is draining the battery continuously even when the truck is off. Only problem is, lots of stuff is powered from that fuse, so without more troubleshooting it's hard to say where the problem is.

Still sound like the alternator isn't charging, for whatever reason. Otherwise the truck would stay running once you got it going.

94_Bama

Thanks for the help, seems like i have a lot of things to trace down on that circuit.. One main cause that i found today is that in the 40A i have a 10 amp fuse so thats not helping at all lol...

RJR

Here's a link to the basic wiring diagram of the charging circuit, so you can see where all AM1 40 goes.
http://personal.utulsa.edu/~nathan-b.../2powersou.pdf