HELP! I am trying to get my truck running. It is a 1990 F-150 I have replaced the fuses, battery, and checked the wiring. I tried to start it a few days ago after driving it for a couple of weeks and wouldn't start. After jumping the battery it started with no plms. I thought maybe I left my door ajar overnight so I went on with my errands and wouldn't start after the stop at the store. Once again it started without fail and I went on driving and then the lights went dim and she started sputtering like being out of gas then nothing. Borrowed a battery charger from my pap and got it home. I read somewhere that I could full field the regulator and see if it was the alternator or just the regulator. How do I full field the alternator?????

 

Give the battery a full charge and take it in for a load test, everyone that sells batterys does it for free. Even Walmart. Don't start playing with anything till the battery is checked out.Remember the charging system is only as good as it's weakest link which is usually the battery. If it checks out get it going and check the charging rate with a voltmeter. There are auto parts stores that have bench alternator testers .........but you have to take the alternator off for them to check it.

 

Autozone can test both batteries and alternators on the vehicle.

 

My battery is a week old and I have charged it on a battery charger twice and it eventually dies. It has to be the alternator but I can't tell in my Haynes manual if the regulator is built in the alternator or if it is separate. My pap told me we could leave the regulator off if it had one and see if it was the regulator or the alternator. It would save me a whole of money if it was.

 

I think your confusing it w/ a generator set up. Just have your alternator bench checked. You can test alternator output on the truck by putting POS lead on the Positive alternator connection & NEG lead to ground. Should be 14+Volts. at Idle.