Not Charging
08-25-2024, 09:44 AM
#1
JK Newbie
Thread Starter
Not Charging
Hello everyone. 2010 JK Rubicon, fairly stock with no electrical modifications with 99K miles.. I had planned on getting the alternator rebuilt due to a bearing whine. Unfortunately, before I had a chance, it died on the way home. At this point the battery light had come on and the battery was dead. I replaced the battery and drove it about 500ft home. I pulled the alternator and I had it rebuilt. Put it all back together, but the battery is not charging. Pulled the alternator and new battery and had them tested and both test good. Checked grounds with my meter, checked lead from alternator to battery and it passes visual and continuity, connections are clean and tight. I measure 11.2 volts directly from the alternator to ground which is what I see at the battery as well. I have a scanner that can see voltage and it reads a similar voltage. The voltage doesn't change with RPM. The belt tension is good. At this point I'm thinking it's time for a new computer, but wanted to see what others may suggest.
Thank you!
Thank you!
08-31-2024, 12:13 AM
#2
JK Newbie
From what you say, I'm going to guess that the voltage regulation is in the ECM on these? That's a little unusual, but not unheard of. I don't have electrical drawings handy to take a look at, so I don't know for sure.
In any event, for an alternator to put out power, it needs to have it's field excited. On internally regulated alternators, a circuit inside the case takes a little power from the battery & makes this happen. On externally regulated alternators, there is a smaller wire that feeds this small amount of power from an external regulator. On ECM regulated alternators, you generally have the same wire, but it just comes from the ECM rather than an external regulator.
I would use a volt meter to see if you have field voltage present at the alternator when the motor is running. If not then trace the wire back & look for a break in the wire, a blown fuse or a bad fusible link. These are general practices & not specific to a Jeep. My JK hasn't had a charge problem yet, so I haven't looked to see what's in there for a charging system. My old CJs had "one wire Chevy Alternators" that had internal regulators. Those regulators were replaceable and cost less than $20 back in the day. You needed to know the tooth pick trick to get the brushes back in after changing the internal regulator in a CJ.
Since ECMs tend to be expensive, if I had a ECM controlled alternator that did not work & the problem was caused by no signal from the ECM, I might be tempted to install an external regulator. They are commonly available & some can still be had for like $20. I've used a Ford external regulator on a Chevy alternator for an inboard motor in a boat before. There is a fair amount of leeway in what you can do & still get something to work.
If you have a local shop that specializes in alternators, you might want to ask those guys for advice.
In any event, for an alternator to put out power, it needs to have it's field excited. On internally regulated alternators, a circuit inside the case takes a little power from the battery & makes this happen. On externally regulated alternators, there is a smaller wire that feeds this small amount of power from an external regulator. On ECM regulated alternators, you generally have the same wire, but it just comes from the ECM rather than an external regulator.
I would use a volt meter to see if you have field voltage present at the alternator when the motor is running. If not then trace the wire back & look for a break in the wire, a blown fuse or a bad fusible link. These are general practices & not specific to a Jeep. My JK hasn't had a charge problem yet, so I haven't looked to see what's in there for a charging system. My old CJs had "one wire Chevy Alternators" that had internal regulators. Those regulators were replaceable and cost less than $20 back in the day. You needed to know the tooth pick trick to get the brushes back in after changing the internal regulator in a CJ.
Since ECMs tend to be expensive, if I had a ECM controlled alternator that did not work & the problem was caused by no signal from the ECM, I might be tempted to install an external regulator. They are commonly available & some can still be had for like $20. I've used a Ford external regulator on a Chevy alternator for an inboard motor in a boat before. There is a fair amount of leeway in what you can do & still get something to work.
If you have a local shop that specializes in alternators, you might want to ask those guys for advice.