Looking for info on hooking up a battery isolator to a 1991 w250 alternator.
I can see the ND symbol on the unit but no other info as amperage which the manual points to 120amp.
I have installed one on a toyota years ago.
But not sure what that little black connection box is on the back of the alternator.
Can anyone help???


Thanks

 

Not sure on the black box, my 93 has it as well. Extermal regulator?? Try a search on the subject and you`ll probably see what you need.

 

these alts are ND's and utilize an external "regulator" on 94+ the regulator is a board, on yours it might be a silver box mounted to the firewall, not sure, but the little black box on the alt is simply the pos and neg field wires from the regulator. Isolators are easy, runa second ouput wire from the alt and hook it to the "A" term on the isolator. Hook the batteries to the 1,2,3......or as many batts as you want to isolate power to. Make sure to get an isolator rated for the output current of your alternator. If not, you'll blow the diodes out of it. I assume this is for a camper battery or the like??

 

I think your alt is a 90 amp and the regulator is external up to 91 then they are built into the BCM. You can install a external regulator on a Alt that has a BCM controled regulator if the regulator gives up the ghost.

 

I really thank you guys for the info, being it's a older dodge and all, turns out the alternator is 120amp and the manual is telling the the black thing is a field generator of some sort.That is all I could find in the manual.
I'm just not sure I want to try and do it with out knowing the corrrect way...Darn alternator is 240.00 to replace......

 

Like got diesel said, isolators are simple. If you buy a new isolator it should come with instructions. Just make sure you know the correct amps of the alt and go about a 20 amp increase on rating so it never gets overloaded on continuous use. Make sure you use the correct guage cables for the max amp load and the length of the run. 120 amp is usually 6 guage for shorter runs and 4 guage for longer runs. The alt output wire is hooked to the isolater in term and the output terms go to the batts and feed wires you want to seperate. Ive installed quite a few and never had a problem.