starter, alternator, or battery?

I have a problem with my fox body. The problem was on my way home from work. My car drove all the way to work fine. No problems. I go to get in my car to leave. It will not start. I hear the clicking sound that means a bad battery. The battery is a week old. Optima 12v battery. my lights would still turn on and my radio would turn on but would not crank. I still just for the hell of it try to jump it. It takes a jump. On my way home, I am at a light, and it kills in the middle of driving it. From this, I would think that would rule out the battery, because if the alternator was good, you should be able to drive your car without the battery so I don't think it is battery. Next. Could the up's have slowed the accessories so much that I need a higher amp alternator? I took the alt to auto zone last week when I had problems, tested it 3 times and it came back good. I tried to tap the starter with a rubber hammer to try to see if it was the starter but it is not even getting past the clicking so I don't think it is the starter. The only 2 electric things I have on the car is a simple cd player and an electric fan. The fan does come on when the key is on the on position. The guy ran it to the ignition. so I pull to the side of the road. I had the cable's back on to try to jump it. Could the alt be going on so that it was not charing the battery back and caused the battery to get low. I know it tested good at auto zone but it might not be enough alt for the up's? any thought of what it could be?
 
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if you are running an E-fan you should have already jumped to the 3g alternator, and from what I have read the underdrive pullies are hard on the charging system unless you are at highway speeds. you could also try the starter relay on you inner fender to see if it is still good. I would then go over all your connections and grounds to make sure that they are free of corrosion and that they are nice and tight. I also noticed that you have an electric water pump. my guess would be that if you have the stock alt. you are at full draw and are not charging your battery. I would go with the 6g alternator. it's smaller than the 3g so it will fit in your bracket with no modifications. it should be more than enough to cover your needs. In the mean time I would put a trickle charger on your battery every night to help keep it full.
 
do you have to install the part # PA-9902 when you install a 3g alt. I read that on brothersperformance.com but it did not say anything like that on 50resto. it is just a wire kit. what kind of modifications do you have to make on the alt bracket to make it fit?
 
you need to do 2 things. 1st check the charging system out put should be 13-14volt range going to the battery anything less no good anything realy high like 16-18 really bad(faulty voltage regulator which is internal). next do a battery load test. fully charge the battery with a battery charger and bring it to parts store and have it load tested, optima's have been known to come of the shelf bad, a friend of mine went through 2 of them before he got one to hold a charge. you want 12v at the battery after it's been sittiing in the car. most auto parts stores will check the charging system for you to, sounds to me like the alt isn't working or the battery wont hold the charge. I'm leaning more towards the alts output, sounds like you where running off the jump to the battery and when the jiuce ran out the car died, sure sign of a bad alternator. best of luck.
 
The alternator will not put out the rated voltage if the battery does not supply sufficent voltage to power the field windings.

Auto Electrics 101: Generators will run without a battery. The iron core for the field coils will retain enough magnetism to create the magnetic field required to make electricity.

Alternators like the ones used on Mustangs require a battery to power the rotating field windings. That's because the AC current they generate internally demagnetizes the iron core for the field coils when there is no battery current to power them. The diodes inside the alternator turn the AC current into DC current. There are 3 phases to the alternator’s internal circuitry & 6 diodes to rectify the AC current into DC current. The battery acts like a big sink or capacitor to smooth out the remaining pulses

Never disconnect the battery from an alternator. The electrical spike produced before the alternator output drops to zero can damage things like the computer, radio and even the alternator itself.

There are some self exciting alternators, but I have never seen one on a Ford or GM car. The last self exciting alternator I worked on was a 200 amp 110 volt one in a Convar 580 twin turboprop airplane. That was over 30 years ago…