Last week my truck wouldn't start. I jumped it off and all was fine. A few days later the battery was dead again. I purchased a new battery and everything was fine. A few days later the battery was dead again. While jumping the truck off It would die after disconnecting the jumper cables. Next I changed the alternator. I still have the same problem. It seems like the alternator is not putting any power into the battery. Can the starter relay cause charging problems if it has gone out?

 

Time to get the vom out. Check the voltage at the big stud on the alt while running should be 14+ volts. If not check for voltage at the green with red striped wire going into the alt shoul show 2-5 volts. If not check all your fuses. If the voltage is there then chances are alt is toast take in and have it bench tested.

 

Original Battery Cables - Charge Cable?

 

Would be wise to include some more info about the truck/engine.

WHAT alternator?
Assuming the 2G (external fan, two plugs, no separate charge cable) I'm going to say the infamous "FirePlug" bit you in the butt.
That rectangular plug (two 10Ga black/orange wires and a white/black) is to be replaced any time the charging system is serviced -per the Ford TSB.

I just made a post about this a couple of days ago, and included a half dozen part numbers for aftermarket suppliers of the pigtail/plug that melts and causes a dead battery or catches on fire.

 

On your 1994 F150 my first guess would be you put a wire or two on the wrong side of the starter relay.

As to your question, NO a bad starter relay on the passengers fender will not cause your 3G Alternator to do this.
Did you change the cluster and then the problem started?

Fuse Link "J" could be open at the starter relay.
Or Fuse "P" under the hood could be open but this is doubtful as it feeds other stuff.

You can try grounding the "F" screw on the back of the alternator with a volt meter on the large stud and see if it charges. Do not run it this way for very long, just long enough to test if it will charge.


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