alternator/charging issue

[strokenit]

i have a 96 f250 with around 90k, CAI, straight pipe, ts chip. well a few months ago my alternator took a dump on my way from TN to IN. voltmeter kept dropping until my truck finally died. changed the alternator and let my buddies car run and charge my batteries while we were working on it in a gas station parking lot. needless to say...the alternator they gave me had the wrong pulley and didn't charge my batteries any while trying to make it on to my brothers and he had to drive to Cincinnati with his trailer and haul me home. had some other stuff going on and just now getting it back and running. however, i purchased a high output alternator and put on it (since i run a plow in the winter and could use the extra boost). my batteries will take and hold a charge from a battery charger, alternator has around 14 volts coming straight from it...but my batteries continue to drain while running and not charge? they had 10-11 volts and i let it idle for aprox half an hour and went back and checked it and they were around 6...tried to back it out of my brothers garage and it died. needless to say...hooked the charger back up over night so i can move it out of his garage and his way. what can i check or what can be causing my batteries to not charge up off alternator?

thanks in advance

[Chop]

I would suggest checking all battery connections and the ground connections from both batteries.I had a small nightmare with my truck and found thru an ohm meter and a jumper cable,the left negative cable mounted to the block was a bit loose.I unbolted it and installed a lock washer,problem solved. With engine running,I attached jumper cable to battery ground and then ground the cable to ac bracket ,volt readings on both batteries instantly improved.

[strokenit]

All battery connections are good. they were removed, cleaned and put back on when alternator was changed. i tried using jumper cables as a new ground and it didn't change anything. however i took a volt meter and was testing on the battery isolator. lt has the 14 volts going to it coming out of the alternator. however, there isn't 14 volts coming out. only one pin registers and it was around 8 volts. does this mean my battery isolator is bad? the original alternator was putting out too much (guess regulator went bad) and maybe it fried it? or any other ideas...shoudlnt it be sending 14 volts out...i don't know anything about them. and if its bad...where can i get one?

thanks again

[Chop]

I am unsure what a battery isolator is ,but you should have at least 12 volts on the positive post on alternator without engine running and at least something in the range of 14 plus with alternator spinning .The voltage regulators on these alternators are built in and too me seem prone to vibration and fail along with the bearings. I did a voltage check thru the power outlet while driving my truck using volt meter,and I saw a wide range of charge.It would mostly stay around 14.5 and climb to 16 volts or more and then return to the 14 s,all this from a new alternator from Delco

[strokenit]

the battery isolator is located on the drivers side firewall of our trucks and is what allows us to charge the batteries in our trucks by only hooking the charger to one side. its purpose is to allow the alternator to charge both at the same time, and also keep the batteries from draining each other. one is the main battery and the other is technically an accessory battery. if one goes bad or gets week...it keeps that one from killing the good one. thats my understanding. i found the local auto parts store has them. what i don't understand is that our stock alternators are 130 amp...its a 95 amp isolator. i bumped my alternator up to a 200 amp alternator to help out with my snow plow...so do i need to bump up the isolator as well? or how does all this work considering it wasn't rated for the stock alternator???

[Chop]

Beats the hell out out of me,Maybe Alberta 7.3 the guru and electrician will chime and help us all with this one !

[strokenit]

haha. i dunno either. but i do aprec the help. i did talk to a buddy of mine half way explained it to me...as far as me typing it...id confuse you and myself trying to explain what he did. all i know is...he said to go with a 200amp isolator to match my alternator. and said when my alternator went out and was pushing too much...it sounds like it fried mine. thats all i know...so guess i gotta cough up some cash to get a new one

[Patrick Feeley]

There is no (or should not be an) isolator in the system. The batteries are simply in parallel. The batteries will charge together when a charger is hooked to one. There is the starter relay on the passenger fenderwell, but that's about it. There is the trailer battery charge relay in the box on the driver's side, but no isolator. Cheers!

[strokenit]

i have a square blue isolator on my drivers side firewall. 95 amp to be exact. I'm the 2nd owner at 26k and purchased from an old man that used it to tow his bass boat with in bed camper to florida every year. needless to say it didn't make many trips as i bought it 2006 and it had 26,6?? miles on it. i know i didn't add the isolator. so how are they supposed to be wired if its not supposed to be there as my alternator goes strait to it? maybe it was added by him for whatever reason...but that i do not know (maybe something to do with the inbed camper??? (as in sleeper camper...not camper shell).

and now that i am typing this...my two main batteries are connected together via one huge cable across front of truck like where hood latches. alternator goes to isolator and now that i think about it...i think it only goes back to one of the batteries as i tried chasing the wires today and looked like one went straight dwn and under truck. so if the isolator was actually being used in between the two batteries...then why would they still be connected???? I'm going to check in morn and see if it doesn't go to the bed of the truck where theres a plug for that camper still located as maybe the isolater was used for something on it maybe????? sorry for any confusion here...just thinking on paper and trying to get an idea on whats going on. would be nice if the isolator is not necessary as i dnt really have $150 for a new one

[97fdexp]

I changed my alternator yesterday and had nothing but problems, 10.1v output. Took it back to O'reillys this morning, it checked good. Brought it home, pulled the batteries, disconnected wiring, all checked good continuity. Decided to just put it all back, jumped the trucked, back to 14.2 charging volts and I didn't do anything but disconnec and reconnect everything, weird!