Battery light on
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New User
Joined: Aug 2014
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From: Bakersfield, CA
Battery light on
I recently helped my dad replace his batteries and alternator on his 2006 F250, with a 6.0. Started the truck, voltage at the passenger side battery and PCM control voltage read a steady 14.1 volts. Battery light still on. Shut off the truck, restarted it, and voltage peaks at 12v.
Any help is appreciated and thanks in advance
Any help is appreciated and thanks in advance
Postmaster
Joined: Nov 2015
Posts: 4,807
Likes: 125
From: Colorado Springs
Grab your multimeter and start by testing your alternator, it's the nut on the back of the alternator, make sure your GP's have shut off. You should see 14.4+. Then remove both batteries and have them load tested. Report back.
Make sure all terminals are clean, use a battery terminal brush i.e. Remove them and clean. Also get the negative cables on the frame.
Make sure all terminals are clean, use a battery terminal brush i.e. Remove them and clean. Also get the negative cables on the frame.
Tuned
Joined: Dec 2017
Posts: 293
Likes: 29
From: Houston
A thorough check with a multi-meter will definitely tell the tale. Just went through a similar exercise with a 2000 gasser, FTE Alt. The root cause of that failure involved a bent "S" male pin in the ASI connector, mechanically difficult to spot and I failed to verify electrically due to my assumption that is was connected since the connector was "plugged in". Lesson re-learned, trust but verify, never assume. Also the PCM controls the dash gauges in many modern vehicles, rendering voltage meters and oil pressure gauges into nothing more than idiot meters,
Token Redneck
Joined: Jun 2007
Posts: 9,335
Likes: 344
From: Breckenridge, TX
Two things: one I agree with him ^^^, check the pins in the connector, I backed one out when I replaced my alternator.
Second, on the driver's side positive connector, check the stud and the 6awg red wire coming off it. If you're reading through the OBDII port that connection is what all the body power passes through.
Second, on the driver's side positive connector, check the stud and the 6awg red wire coming off it. If you're reading through the OBDII port that connection is what all the body power passes through.
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New User
Joined: Aug 2014
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From: Bakersfield, CA
Batteries were load tested a couple days before we changed the alternator. A new, OEM positive wire (battery to battery to starter) was replaced with the batteries (which were replaced last month before a trip to Denver, Co.). Measured voltage at the alternator post; 12v. Watched the truck warm up to 175, no change in reading, as I measured it multiple times. The alternator is a reman 140, which we (my dad and I), have heard that the reman alternators are hit and miss.
Postmaster
Joined: Nov 2015
Posts: 4,807
Likes: 125
From: Colorado Springs
Batteries were load tested a couple days before we changed the alternator. A new, OEM positive wire (battery to battery to starter) was replaced with the batteries (which were replaced last month before a trip to Denver, Co.). Measured voltage at the alternator post; 12v. Watched the truck warm up to 175, no change in reading, as I measured it multiple times. The alternator is a reman 140, which we (my dad and I), have heard that the reman alternators are hit and miss.
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New User
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From: Bakersfield, CA
Yeah, I had a feeling it would continue to be the alternator. Now, how long do the glow plugs stay on, or is it dependent on the temprature?
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Tuned
Joined: Dec 2017
Posts: 293
Likes: 29
From: Houston
Colorado350 is totally correct. Never disc any alternator on any running vehicle, with modern vehicles the penalty can be very expensive. Sounds like your alternator may indeed be a dead duck, out of curiosity what is the I terminal and S terminal voltage with engine running? (With engine running, I being normally ~ 12 V but going low due to alt failure, providing ground leg for red dash light and S normally being ~ 6 V)
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New User
Joined: Aug 2014
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From: Bakersfield, CA
Jetty, I'll have to check tomorrow, as the truck is my dads and is at his house. Also, rest assured I won't disconnect the batteries while the truck is running, I don't want to get stuck with replacing the FICM or any other control module for that matter lol.
Token Redneck
Joined: Jun 2007
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From: Breckenridge, TX
https://www.ford-trucks.com/forums/1...l#post17256706
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New User
Joined: Aug 2014
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From: Bakersfield, CA
Thanks everyone for the help. Found the replacement alternator to be faulty. Got another one, and had the auto parts store check it before we left. It passed, took it and put it on, and VOILA! Back to normal.
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