New starter & Alternator, Battery loses charge

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Old Nov 14, 2010 | 08:55 AM
  #1  
JohnnyThrowback's Avatar
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New starter & Alternator, Battery loses charge

1999 F150, 4.2L V6.

This past Tuesday, my starter gave out. My mechanic installed a new Remy starter and the wiring harness between the starter and the battery. The truck ran fine for one day. Then, while driving (fortunately) about a mile from my home, suddenly the radio and all of the instrument panel gauges shut down. The engine kept running and I limped home, expecting not to be able to restart the engine once I shut down. Unfortunately I was correct. However, after allowing the truck to rest idle for an hour or so I was able to restart it, but again everything shut down shortly thereafter and could not retart until after another "rest".

I noted that when I turned the headlights on and turned the crank, my headlights went out. I then suspected the alternator. I replaced the alternator yesterday with a new Remy 130 amp alternator. I was able to start the vehicle instantly, but now the battery light came on.

I checked the voltage on the battery with then engine off, and it was a little shy of 12V (around 11.50). When I turned the engine on, I noticed the voltage slowly dropping, which tells me that the alternator isn't charging. I boosted the battery overnight in order to get to 12 V, but noticed the same voltage drop this morning when I turned on the engine.

One thing I noticed is that the ground wire from the wiring harness coming from the alternator was not connected to anything at the time I lifted the hood after my gauges shut down (i.e. after new starter, before new alternator). When I installed the new alternator I made sure to connect this ground wire to a screw near the starter relay firewall.

Any help you can provide will be appreciated!
 
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Old Nov 15, 2010 | 03:26 AM
  #2  
code58's Avatar
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From: So. Cal.
Originally Posted by JohnnyThrowback
1999 F150, 4.2L V6.

This past Tuesday, my starter gave out. My mechanic installed a new Remy starter and the wiring harness between the starter and the battery. The truck ran fine for one day. Then, while driving (fortunately) about a mile from my home, suddenly the radio and all of the instrument panel gauges shut down. The engine kept running and I limped home, expecting not to be able to restart the engine once I shut down. Unfortunately I was correct. However, after allowing the truck to rest idle for an hour or so I was able to restart it, but again everything shut down shortly thereafter and could not retart until after another "rest".

I noted that when I turned the headlights on and turned the crank, my headlights went out. I then suspected the alternator. I replaced the alternator yesterday with a new Remy 130 amp alternator. I was able to start the vehicle instantly, but now the battery light came on.

I checked the voltage on the battery with then engine off, and it was a little shy of 12V (around 11.50). When I turned the engine on, I noticed the voltage slowly dropping, which tells me that the alternator isn't charging. I boosted the battery overnight in order to get to 12 V, but noticed the same voltage drop this morning when I turned on the engine.

One thing I noticed is that the ground wire from the wiring harness coming from the alternator was not connected to anything at the time I lifted the hood after my gauges shut down (i.e. after new starter, before new alternator). When I installed the new alternator I made sure to connect this ground wire to a screw near the starter relay firewall.

Any help you can provide will be appreciated!
You do realize that a 12V battery runs 12.6-12.8V at full charge don't you? A 12V battery at 11.5-12V is technically DEAD! The 1st thing I would do is charge the battery to full charge (which should be AT LEAST 12.6V) and then have it LOAD TESTED. If you can't get it to charge to at least 12.5V (and stay there), you need a new battery also. THEN try and diagnose the problem, IF you still have it.
 
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Old Nov 17, 2010 | 07:00 AM
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My guess is the new wiring harness is missing a ground connection or is shorting out somewhere.
 
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Old Nov 18, 2010 | 11:57 AM
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Turns out I blew the fuse for the charging system. Duh. Fortunately a very easy and cheap repair.
 
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