Hey,
I have a 94 F350 Centurion Crewcab with the 7.5L V8 that has some sort of slow battery drain. I put a brand new battery in it about three weeks ago. I would start it every couple of days with no problem, the battery gauge would be right up where it needs to be when its running...thats what is making me rule out the alternator. I went to start it two days ago and just got clicks.....Any ideas???? The thing that really sucks is that this thing has bells and whistles out the ying yang...so it could be ANYTHING. Any suggestions would be appreciated.

 

what it sounds like to me is that battery is going bad, my truck did almost the exact thning you describe, i tested the alt and that worked well, so i checked the battery and it was found that at least two cells were bad and no longer holding a charge properly.

 

ehh, I'm leaning away from that because I placed a brand new battery in it when I got it three weeks ago. The guy that gave me the truck told me there was a drain somewhere, so i put in a new battery to monitor that...sure enough there is. I've been told it could be a bad battery cable as well.

 

thats another possibility

 

Get yourself a multimeter and put it across the battery terminals with the engine off, you should get 12.5v. Now start the motor and you should see 13.5-14v and if so this confirms the alternator is charging. If you still only have 12.5v then the alt is not charging and the problem could be a bad bridge rectifier or voltage regulator.. both of which are inside the alternator and can be changed without replacing the alt. Also note that these devices often test OK at the parts store on those desktop alternator testers so this test is actually better. There is also a fusable link in the charging system that could be open, and the circuit goes through the dash cluster to the voltage gauge so it too will affect battery charging.

Hopefully the alternator or one of its internal components is your problem because if it's not and the battery still goes dead then you have an errant current draw somewhere that you will have to track down by isolating every circuit in the truck one at a time.