Alternator wiring question?
01-22-2010, 05:19 PM
#1
Rennlist Member
Thread Starter
Join Date: Oct 2002
Location: Florida Space Coast
Posts: 95
Likes: 0
Received 0 Likes
on
0 Posts
Alternator wiring question?
Hi folks,
Back to troubleshooting the battery not charging. Had this issue awhile ago and a regulator/brushes replacement seemed to fix the issue. Or so I thought. The last day of driving up here in NE my car did the Christmas tree lights thing and died. Got help from fellow RENNLISTER DeadEye and got my car home. Thanks Dennis. Again, the battery isn't getting charged by the alternator. Using a battery charger, the battery charges. It will hold a charge under load (car starts, lights on and it holds voltage at about 11.8v). Battery is only 3 months old. Had the alternator tested and it too checked out fine. So, the question is. Of the 3 wires connected to the alternator, the red and brown (12v and gnd) I think I know. What is the 3rd wire and how do I check out the wiring?
Thanks,
Jeff
Back to troubleshooting the battery not charging. Had this issue awhile ago and a regulator/brushes replacement seemed to fix the issue. Or so I thought. The last day of driving up here in NE my car did the Christmas tree lights thing and died. Got help from fellow RENNLISTER DeadEye and got my car home. Thanks Dennis. Again, the battery isn't getting charged by the alternator. Using a battery charger, the battery charges. It will hold a charge under load (car starts, lights on and it holds voltage at about 11.8v). Battery is only 3 months old. Had the alternator tested and it too checked out fine. So, the question is. Of the 3 wires connected to the alternator, the red and brown (12v and gnd) I think I know. What is the 3rd wire and how do I check out the wiring?
Thanks,
Jeff
01-22-2010, 07:23 PM
#2
Rennlist Member
A good read on alternator function here ...
the 3rd wire is likely the reference B+ voltage to the regulator: with sufficient voltage drop, the regulator switches on/off controlling the energizing current to the rotor .... which controls how much juice the field coils toss out to the battery ( @ ~ 14.4V).
The B+ ( ~12.6V for a good battery) feed via that 3rd wire usually comes from the X-bus/load reduction relay. If there is a problem here, an otherwise good alternator will not know how to regulate properly.
the 3rd wire is likely the reference B+ voltage to the regulator: with sufficient voltage drop, the regulator switches on/off controlling the energizing current to the rotor .... which controls how much juice the field coils toss out to the battery ( @ ~ 14.4V).
The B+ ( ~12.6V for a good battery) feed via that 3rd wire usually comes from the X-bus/load reduction relay. If there is a problem here, an otherwise good alternator will not know how to regulate properly.
