ok, yesterday i was taking my room mate to work, so we jump into my truck (98 supercab F150, 4.6) it started a little slower than usual. not to uncommon in the cold, it was raining, so i turn on the wipers... they are moving really slow thats odd. i look at my voltage guage and it was reading like about 9-10, so i turned off the radio, and figured it would charge if i just drove it a lil... no luck, just got progressively worse, i tried flooring it to see what it would do.. and all it did was bog down and not really do much, so i get going further down the road, now the guages are dimming off, and it's just driving worse and worse, so i pull into a parking lot and then the tach and all other guages just stop working completely but the truck is still running and eventually it just shut off... so i tried to start it up again.. and it makes a noise like a fast clacking. so i have no idea what the hell is wrong with it because the day before it ran perfect. i'm charging the battery to see if that is the prob. otherwise what else is it? starter? alternator? help me out guys i'm pretty good with cars/trucks but i'm stumped on this one cuz i've never heard those kinds of noises before from a vehicle trying to start...

 

Clearly, the way you describe it sounds like it's running off the battery, until it dies.

Sure sign the alternator is bad.

If you keep charging the battery and driving you will ruin the battery, also.

Edit to add: The noise is normal for a "dead battery", trying to crank the truck.

 

I don't know much about engines, but to me it sounds like a bad battery.

edit---guy above me sounds right!

 

I bet the battery is fine, your alternator is going out. Normally the alternator will charge the battery as systems pull a charge from the battery, but if the alternator is bad then it cant charge the battery, so the battery gets drained and there's no power for all the electronics to run off of.

Get your alternator looked at, once you charge the battery it should be fine again.

 

Unless something weird is going on, I'd agree with the others that it is the alternator. Your battery did its job untill it ran dead, so it's probably fine. Napa will do a alternator test if you bring it in to them.

 

yeah, it was the alternator... 145 bucks, now it's fine..

 

you're bad luck. My alternator went out yesterday. Thanks!!!