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Old 07-21-2014, 09:15 AM
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Battery light coming on after starting

HELP!! I've been fighting this for almost 2 years. My '04 6.0 was built in July of '03. It has the single alternator is very stock. It has only 52,300 miles and I have a scan gauge on it. 3 years ago the light kept coming on and I was able to determine that the belt was old and slipping. I changed it and the light stopped coming on. Almost 2 years ago, it started again. Here is what it is doing:
Start the truck in the morning. Voltage on the scan gauge reads about 11.7 for about a minute. Bumps up over the next 2 minutes to 12.8 / 13.5. Settles in at 13.8 to 14.2. I only drive 2.9 miles (about 10 minutes) to work. I know this is not good on the system. The light will go off and on a couple of times. I leave 3 to 4 hours later and the same thing. When I drive a greater distance (more than 10 miles) it will stay off. I drove home last night (104 miles) and 12 hours later, the light came on this morning. I will be checking the idler pulley this week. It may be that it's dragging until it gets hot.
Here is what I have done:

1. Had the alternator tested. Good
2. Swapped the alternator with a rebuilt. No change, put the original back on
3. Pulled the batteries (2 years old) and had them load tested. Good
4. Charged the batteries all night. No change

Does anyone have any ideas what else to look for???
The only other thing I have done is have the ficm rebuilt with an output of 54.5 volts.

Thanks!!!
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Old 07-21-2014, 09:23 AM
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Quote:
Originally Posted by timewarp1934 View Post
HELP!! I've been fighting this for almost 2 years. My '04 6.0 was built in July of '03. It has the single alternator is very stock. It has only 52,300 miles and I have a scan gauge on it. 3 years ago the light kept coming on and I was able to determine that the belt was old and slipping. I changed it and the light stopped coming on. Almost 2 years ago, it started again. Here is what it is doing:
Start the truck in the morning. Voltage on the scan gauge reads about 11.7 for about a minute. Bumps up over the next 2 minutes to 12.8 / 13.5. Settles in at 13.8 to 14.2. I only drive 2.9 miles (about 10 minutes) to work. I know this is not good on the system. The light will go off and on a couple of times. I leave 3 to 4 hours later and the same thing. When I drive a greater distance (more than 10 miles) it will stay off. I drove home last night (104 miles) and 12 hours later, the light came on this morning. I will be checking the idler pulley this week. It may be that it's dragging until it gets hot.
Here is what I have done:

1. Had the alternator tested. Good
2. Swapped the alternator with a rebuilt. No change, put the original back on
3. Pulled the batteries (2 years old) and had them load tested. Good
4. Charged the batteries all night. No change

Does anyone have any ideas what else to look for???
The only other thing I have done is have the ficm rebuilt with an output of 54.5 volts.

Thanks!!!
My light used to come off and flicker at times. My problem was the 3 or 4 wire plug on top of the alternator wasn't making a good connection. New plug been good to do since

Sent from AutoGuide.com Free App
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Old 07-21-2014, 09:56 AM
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Thanks!!! I will take a look at it today and will post what I find!
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Old 07-21-2014, 10:02 AM
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Your voltage regulator is bad.

It is built in to the alternator so the whole thing needs to be replaced.

Having it load tested by an auto parts store does nothing.

Replace the alternator with ONLY a Motorcraft or a specialty builder like DC Alternators.

DO NOT BUY AN ALTERNATOR FROM AN AUTO PARTS STORE!!!
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Old 07-21-2014, 11:02 AM
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Hi, Thanks! I bought a new regulator about 6 months ago and did not install it. I tried a rebuilt alternator before installing the regulator and it did not help. I guess the rebuilt may have been bad. I've heard they are real hit and miss. I will check the plug today and then install the regulator asap. Thanks again!!
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  #6  
Old 07-21-2014, 11:18 AM
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Quote:
Originally Posted by timewarp1934 View Post
Hi, Thanks! I bought a new regulator about 6 months ago and did not install it. I tried a rebuilt alternator before installing the regulator and it did not help. I guess the rebuilt may have been bad. I've heard they are real hit and miss. I will check the plug today and then install the regulator asap. Thanks again!!
That's why I suggested an alternator from Motorcraft only or a new specialty build.

New and rebuilt alternators from part stores straight up suck!

I had 3 new Autozone alternators that were bad right out of the box!!!

And the current one that finally worked is giving me issues right now.

So don't waste your money on the part store crap and just go with a Ford.
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Old 07-22-2014, 08:41 AM
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Yes. I worked for a Ford dealer in the late 70's and prefer OEM. I normally have my parts rebuilt. They're tested before I get them back. I had my alternator tested at the local starter / generator shop about 2.5 years ago and it was fine. I checked the plug on the alternator and all looked well. So now it's on to the voltage regulator. "The more you know about what it isn't tells you more about what it is". Do you know if the sensor was a "real time" unit? Thanks
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Old 07-22-2014, 08:50 AM
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Just a suggestion - check your belt tensioner assembly to see if it's holding the belt tight enough.
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Old 07-22-2014, 09:21 AM
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the diode/regulator swap looks like a pain I have one sitting in a box ready to fix my old failed alternator also

your voltages look normal does the reading change when the light comes on ??

mine was dropping a diode intermittently it would test good but the light would come and go I could see the voltage drop on my monitor when the light would come on

a new DC power fixed that
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Old 07-22-2014, 10:02 AM
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Quote:
Originally Posted by ZMANN View Post
a new DC power fixed that
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