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So I recently just replaced my alternator because my batteries were not getting a full charge. I put on a 140 amp for a replacement my question is the same thing is happening that was before I put a new one on. When I start the truck my volts drop down to around 11.4 and it also seems like it has a hard time turning over because of low voltage. Also when I check my batteries there never over half full and there brand new die hard platinum's so I'm sure its not the batteries. I guess my question is what else could be causing this? Or do I need to try another alternator?
 

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Disconnect your batteries, put them on a slow charge, loud test them after they are charged. Dont expect the alernator to fully charge them if they are in bad condition to start with.

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Check all the cable connections, maybe your starter is takin a chit.

Sent from my phone that somebody didn't help me get.
 

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Put a clamp-on ammeter on the charge wire and see what amps you are getting when you startup. I bet you will be a little surprised at what you see.

Bottom line, I don't think you have a huge problem - at least not based solely on an 11.4V reading. It is a little low, but MANY systems drop to 11.7 range on start-up. You aren't off by that much. Maybe the glow plug system is taking a little more juice than most.
 

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Put a clamp-on ammeter on the charge wire and see what ampos you are getting when you startup. I bet you will be a little surprised at what you see.

Bottom line, I don't think you have a huge problem - at least not based solely on an 11.4V reading. It is a little low, but MANY systems drop to 11.7 range on start-up. You aren't off by that much. Maybe the glow plug system is taking a little more juice than most.
Yea, you are correct, I was thinking about the op saying his batteries, seemed low and his starter may be dragging, possible shorting out and draining his batteries. I dunno?

Sent from my phone that somebody didn't help me get.
 

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could be a starter dragging, could be a belt slipping a little also (depending on how long the low voltage reading lasts)
 

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