So my 92 4.0 has been having excessive battery drain when running. Thought it was the alternator just not charging, swapped in a brand new one and a brand new battery, same problem.
What could it be? One day the check engine light came on, code 47. Since then it's been waayyyy down hill.
Its been jumped, charged, driven around and it'll die in about 4 or 5 minutes.
Please help, it's my only means of transportation.

 

Sounds like you have a short somewhere, or a bad ground. Sorry if that's vague, a lot of different places that could happen.

 

Disconnect a battery cable. Put an ammeter or test light in series with the cable and battery terminal. (Leave the ignition switch off.) Does the meter show current flow (or the test light glow)? Then you have something drawing current. Pull the fuses one at a time, and when the current stops flowing, that's the circuit to troubleshoot.

 

I'd start with testing battery voltage at idle...

If the alternator is working the Jeep shouldn't die.

 

I don't recall for sure, but did the Jeep come with a fuseable link between the alternator and the battery. A lot of vehicles use to. If this link is bad then the alternator will not charge the battery. I can think of no other reason why a battery would go dead while the engine is running. If there is no fuesable link in that charging wire then you just have a bad connection between the two.

 

Testing battery voltage at idle would tell.

No fusible link.

 

I took it to advance and they did this. We watched as it steadily went down.

 

A current draw is not going to effect your voltage while the engine is running as long as the alternator is working properly.

If you saw a steady voltage drop with the engine running then your alternator is not putting out. You need to OWN a 12 dollar multi meter so you can do this simple check for yourself.

One lead on ground and the other lead on the positive post on the alternator. It should read at least 13.5 volts. If it reads less than that then your alternator is not working.

I've seen a **** load of bad alternators straight out of the box.

 

I haven't gotten around to getting the voltage tested, as I would need someone to pull me to advance and I'm tired of spending money in things so I don't want to buy a multimeter. I know a multimeter will be very useful, but I've spent too much already.

Just installed new battery cables, same issue.

 

Yet you're still blindly throwing money at problems without proper diagnostics?

You wouldn't be broke if you had that cheap multi meter and you looked into this correctly.

 

Have you got a test light maybe ? See if You got current at big post on back of alternator .....

 

I had already purchased the battery cables and planned on putting them in before this issue first appeared.

 

I just hate seeing people throw money at problems without actually diagnosing the problem.

 

Well I'm going to have a friend pull me to advance tomorrow and have them test it.

 

Pull the alternator out. At least save yourself the trouble of flat towing your truck.