Alternator, battery, or electrical?

80

Asked by Feb 14, 2015 at 10:19 PM about the 1996 Ford F-150

Question type: Maintenance & Repair

My truck had been running fine, until a couple of days ago. It started fine, all gauges reading normal (I'm a habitual and constant gauge-checker). I was out running errands, and after driving for a couple of miles, turned off the truck, and when I went to start it again, just got the "click." Well, I'd been having some issues with the neutral safety switch, but this felt like a battery issue. I checked the terminals, and the positive was a little loose, so I tightened it up, jumped it - it started right up - and after checking the gauges to make sure all was well went on my way. After a couple of miles, the engine shut off - as though you'd turned the key - and then popped right on again! (When it was off, all gauges were dead and so was the engine. It came back on - all the way, gauges and everything - within about a second.) I parked it, let it sit, and jumped it again. Same thing: Started right up, all systems go, only this time the lights, gauges, and everything but the engine shut down, with the engine finally dying after maybe another mile or so. Fine. Towed it home. Replaced the lead from battery to starter (it was a little worn), tried it again. This time I noticed that when the jumper cables are hooked up to the battery, the alternator gauge shows charging - and a little higher than usual, as I would expect. As soon as the jumper cables are disconnected, the alternator gauge shows zero (all other gauges showing appropriate levels), and the engine dies almost immediately.

11 Answers

1,105

First thing I'd do it take the battery and alternator out and take it to a parts store like advance auto parts and them test them just to rule them out. There is also a fuseable link on the positive battery cable, if that fails then the alternator can not charge the battery. To check the fuseable link you need a volt meter. Pierce the cable at either end with the volt meter leads with the engine running it should show at least battery voltage 12.5 volts. If no voltage is present then the positive battery cable must be replaced. If all three of them check out then check your starter solenoid if it's fender mounted. I have seen on some f150's where the post for the solenoid breal off inside the solenoid and caused an open circuit and shut the vehicle off. If everything is tight and the post on the solenoid do not wiggle Then you have an electrical problem or pcm (powertrain control module) problem.

4 out of 4 people think this is helpful.
17,315

Your alternator is bad. Take it off and have it tested

4 out of 4 people think this is helpful.
80

Thanks to both of you. I was thinking it was the alternator, but I'm thrown by the positive reading on the gauge when the jumper cables are attached. After perusing other posts, I'm going to check all related connections, try it again, and if the problem persists, the alternator is coming off. Thanks!

17,315

It's reading the voltage of the other vehicle when the cables are attached

2 out of 2 people think this is helpful.
4,765

Your battery is probably good unless you have run it down trying to start the truck. If so, just give it a good overnight slow charge. From your description it sounds like the whole problem is alternator.

1 out of 1 people think this is helpful.
80

Andrew: I thought maybe that was what was happening, but I didn't know if that was possible. Thanks for confirming my suspicions!

80

Follow-up: I decided to have the battery charged while I was switching out the alternator, and after I'd gotten the new alternator installed, I went back to the parts store ( where I'd left the battery) and they informed me that the battery was bad - it had a bad cell. Wondering if I'd needlessly installed a new alternator, I had them test the old one. It was basically fried: Several internal components were completely shot. It's worth noting that there was absolutely no sign of any damage whatsoever to the naked eye: No scorching, nothing. Nonetheless, it was totally destroyed. From reading other posts and other research, I'm guessing what happened is that the cell in the battery went bad, and then the alternator fried itself trying to maintain a charge in a bad battery. For anyone doing their own research: Again, despite the fact that there were no visible signs of damage to the alternator externally, it was in fact totally shot. I replaced both the alternator and the battery, and all is well. Again, for those of you who are researching: This was an incredibly simple and easy fix. The 1996/7 Ford F-150 is an easy engine to work on, especially regarding this specific issue and others like it. Finally, my sincere thanks to those of you who so graciously took the time and made the effort to offer your advice. I greatly appreciate it, and am pleased to say that my truck is back up and running, which means my grandfather's cattle have enough hay to get through the next few weeks.

6 out of 6 people think this is helpful.
80

One final note for those of you who are researching your own problems: If you're thinking "well, how am I supposed to know if or when a cell in my battery goes bad?" Here's the thing: It turns out that the battery was 13 - yes, thirteen - years old! Of course, had I known that, I'd have put a new one in long ago, and more than likely this wouldn't have happened. My advice - and I'm not an expert, but based on what I've read - is to change your battery if it's 5 years old or older, or at the very least take it in and get it tested. Your local parts store will do it for free. And always keep in mind that no matter how we may try to prevent things like this from happening: Life is unpredictable, and sometimes bad things happen. Good luck!

2 out of 2 people think this is helpful.
4,765

You figurred it out. The battery celll went bad and then the Alternator blew the diods trying to keep it going. If this is not a daily driver, you might want to consider getting a Battery Tender, I have one on me tractor, classic cars and spare battery. Well worth the money. Glad you got it fixed.

20

Same thing happened to me so I bought a new alternator and drove it for a couple days and then all of a sudden the battery gauge when right to zero and shut the truck off.

2 out of 2 people think this is helpful.

Question - I am having similar problems with me 2004-F150. At first, I thought it was just a bad battery. I replaced it - it was over 5 years old anyway. Two days later I go out and it is completely dead. Now I am thinking it is the alternator. I had it checked at Auto Zone and they said it was OK. I am having problems with the electrical system at the same time - radio not working, radio playing but not lights on the radio, Heat will not adjust and a few other things. Do I have a bad alternator? Or do I have electrical problems/fuse problems?

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