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2013 Not Exciting Alternator!!

2K views 6 replies 3 participants last post by  plano-doug 
#1 ·
What could be the issue? 3 alternators and all have the same issue, charge for 5 minutes after start up at 14.7, before gradually decreasing to 12.8! My previous battery was killed by this, now my new battery looks like it will have the same fate if I don't fix this!

I understand the alternator voltage regulator is in the alternator itself but why wont my car excite the alt to keep it charging? My new battery has gone from 13.0v float to 12.5 in a week. Also I have upgraded to a mechman alt and it hasthe same issue!
 
#2 ·
Someone correct me if I'm wrong...but doesn't the voltage demand come from the ECM/PCM? I know the regulator is in the alternator, but I thought it was controlled through the ECM still. Could be wrong though. At any rate, I would try cleaning all the related grounds and make sure they are tight. Trace all the wires coming from the alternator as best as possible, making sure there are no breaks or loose connections.
 
#5 ·
What could be the issue? 3 alternators and all have the same issue, charge for 5 minutes after start up at 14.7, before gradually decreasing to 12.8! My previous battery was killed by this, now my new battery looks like it will have the same fate if I don't fix this!
Besides this observation of the voltage, are you having any other symptoms with the new battery? Are you getting no-crank conditions requiring a jump?

I poked around on this some, and found that the BCM monitors the battery current and sends that info to the ECM which in turn controls the alternator.

The voltage levels you cite are all within the normal operating range for the system. It's normal for the voltage to go up and down.

If you'll PM me your email address, I'll send you the "charging system description" I found.

Doug

.
 
#6 ·
Besides this observation of the voltage, are you having any other symptoms with the new battery? Are you getting no-crank conditions requiring a jump?

I poked around on this some, and found that the BCM monitors the battery current and sends that info to the ECM which in turn controls the alternator.

The voltage levels you cite are all within the normal operating range for the system. It's normal for the voltage to go up and down.

If you'll PM me your email address, I'll send you the "charging system description" I found.

Doug

.
After new battery went in no sluggish start, before it would. It was an agm battery too.
 
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