Alternator woes.. good news/bad news.

Gollywomper

Gollywomper

Professional pot stirrer
Supporting Member
Joined
Feb 9, 2019
Messages
3,530
Location
Corning CA
Bad news I think my alternator took a crap. Good news it’s in my drive way and not on a trail.

My battery died after rotating my winch 6 revolutions to start the wind on my rope. Had to jump start my rig. Alternator is only putting out 12.60 volts. When I rev the engine it goes up to 13.2. I know they are controlled by the PCM. It looks like the alternator is being turned on and just not putting out the amps. Anything to check before replacing the alternator?
 
Last edited:
Gollywomper said:
Bad news I think my alternator took a crap. Good news it’s in my drive way and not on a trail.

My battery died after rotating my winch 6 revolutions to start the wind on my rope. Had to jump start my rig. Alter mayor is only putting out 12.60 volts. When I review the engine it goes up to 13.2. I know they are controlled by the PCM. It looks like the alternator is being turned on and just not putting out the amps. Anything to check before replacing the alternator?
Click to expand...
I’ll try not to be a smart ass with your auto correct
I killed my battery using my winch. I’d test the battery. I really like my Duralast gold battery I got. I’ve used my winch more with this battery than with the other.
I haven’t killed it using it and I do use some revs during and after use
 
Thunderhead said:
I’ll try not to be a smart ass with your auto correct
I killed my battery using my winch. I’d test the battery. I really like my Duralast gold battery I got. I’ve used my winch more with this battery than with the other.
I haven’t killed it using it and I do use some revs during and after use
Click to expand...
I really only bumped the winch twice to get the rope started. It wasn’t enough to draw the battery down. I have a enersys odyssey battery. The alternator should be putting out 14 bolts not 12.6 At idle. Just read the PCM horror stories and was a bit nervous.
 
  • Like
Reactions: Thunderhead
Gollywomper said:
I really only bumped the winch twice to get the rope started. It wasn’t enough to draw the battery down. I have a enersys odyssey battery. The alternator should be putting out 14 bolts not 12.6 At idle. Just read the PCM horror stories and was a bit nervous.
Click to expand...

Load testing your battery is free
I get your concern about the the readings. We have volt readings on our semi trucks for the lift gates so if the tractor isn’t grounded right the batteries for the lift gate won’t charge.
I’d still start with the battery since it won’t matter what your alt is putting out if the battery won’t charge
 
So like if my tractor is reading 14 volts and the lift gate reading is less than 12.4 it not charging them. The LG batteries need to be 13+ to charge but there is a negative connection issues on those that your TJ doesn’t have but …. same principle?
So we replace batteries more than alternators
 
Gollywomper said:
I really only bumped the winch twice to get the rope started. It wasn’t enough to draw the battery down. I have a enersys odyssey battery. The alternator should be putting out 14 bolts not 12.6 At idle. Just read the PCM horror stories and was a bit nervous.
Click to expand...

Mine definitely doesn't do 14, but it's better than 12.6. I think mine is in the 13.4 range.

I've noticed my battery isn't as resilient as the one in my previous TJ. It has a bunch of terminal corrosion so it's probably old, and if I have a project that takes the LJ out of service for two weeks I have to charge the battery to start it. I've been wanting to get a new battery but now you've got me questioning my alternator, too.
 
I need to check my voltages again tomorrow. I didn’t check the alternator output until after I had completely wound up my winch rope under a load. There is a chance my battery got warm and the PCM reduced the output.
 
  • Like
Reactions: freedom_in_4low
200.gif
 
Curiosity got the best of me. I just checked voltage again. At idle it is up to 13.3. I know the battery is not charged properly so I set a small charger up overnight. Will see what the voltages are tomorrow.
 
  • Like
Reactions: freedom_in_4low
Let my little trickle charger run all night. Fired up a cold battery, alternator output this morning was 13.98 at idle. These PCM controlled alternators are a bit different, too smart. Could be a battery, need to load test and see.
 
Gollywomper said:
Curiosity got the best of me. I just checked voltage again. At idle it is up to 13.3. I know the battery is not charged properly so I set a small charger up overnight. Will see what the voltages are tomorrow.
Click to expand...
Your alternator output should be roughly 13.5v to 14.5v
 
flyinfish said:
Your alternator output should be roughly 13.5v to 14.5v
Click to expand...
Yes that’s what it should be. However there is a temp sensor under the battery. When the battery gets warm/hot the PCM reduces the output of the alternator. I think my battery got hot after I jump started then wound my winch up under a load. Charge voltage this morning was 13.98 at idle. So I still have some investigating to do.
 
  • Like
Reactions: flyinfish
Reinstalled battery. Checked for parasitic draw. Had 400 milliamperes which is ok. When I first check I had battery voltage between the negative cable and battery terminal. I found my key switch allows the key to be removed with the key in ACC. So there is a chance I left the radio on. So I need to replace the key switch. And will see how things go. Might even duplicate the acc on to see if it drains the battery and duplicates my issue. Alternator is putting out 14 volts.
Also cleaned my terminals and dash volt gauge now reads slightly above 14 bolts like normal at idle. Time will tell over the next couple days.
 
  • Like
Reactions: Thunderhead
Top Bottom
Back