NEED ADVICE!
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NEED ADVICE!
Okay I have a Ford F-250 4WD Extended cab 5.4 engine....i am having problems with the charging system or SOMETHING! My headlights are very dim...and the battery goes DEAD! Soo i was told my alternator was bad...i replaced the alternator...got a new battery....still nothing! Sooo i got new battery cables pos and negative...replaced the WHOLE cable dat runs to the starter and everywhere else....jump started the truck...it started... I let it run for 1 hour and took it for a test drive...it was fine...but started noticing my interior lights were dim and i started losing power...the truck died! Had it jumpstarted again...it starts but when u take ONE cable off...the truck dies! WAT could be going WRong! 
Cargo Master
Joined: Sep 2007
Posts: 2,624
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From: OR and UT
Sounds like you may have gotten a bad "new" alternator (it has happened before). Did you have the old alternator tested before replacing it? As you probably know, the truck should run without the battery connected because the battery is only used to start the engine.
You might take it to an automotive electric repair shop and have them diagnose the problem, many will do it for no charge.
You might take it to an automotive electric repair shop and have them diagnose the problem, many will do it for no charge.
Senior User
Joined: Dec 2010
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did u ever try acutally measuring the voltage and amperage that the alternator is putting out? or the cold cranking amps the battery is putting out? its usually a good idea to test stuff before just replacing everything
Posting Guru
Joined: Aug 2007
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From: Canton, IL
Sounds like you may have gotten a bad "new" alternator (it has happened before). Did you have the old alternator tested before replacing it? As you probably know, the truck should run without the battery connected because the battery is only used to start the engine.
Edit: Sorry. Thinking in 7.3L land...... still, the PCM will eventually not operate when the voltage drops too low at idle when the alternator is barely charging.......
Posting Guru
Joined: Aug 2007
Posts: 1,714
Likes: 1
From: Canton, IL
Okay I have a Ford F-250 4WD Extended cab 5.4 engine....i am having problems with the charging system or SOMETHING! My headlights are very dim...and the battery goes DEAD! Soo i was told my alternator was bad...i replaced the alternator...got a new battery....still nothing! Sooo i got new battery cables pos and negative...replaced the WHOLE cable dat runs to the starter and everywhere else....jump started the truck...it started... I let it run for 1 hour and took it for a test drive...it was fine...but started noticing my interior lights were dim and i started losing power...the truck died! Had it jumpstarted again...it starts but when u take ONE cable off...the truck dies! WAT could be going WRong!
I bet that your new battery is dead. If you check it, should read 12.8 and not vary by more than .2V (2/10th's). If the battery is OK, you have a bigger problem (read: short to ground.) If it's dead (under 10 volts). that indicates a charging problem for sure. I say repeat the test, charge the battery overnight, then drive till its dead. IF this actually happens, it's definintley something with the alternator.
easier yet: get a digital volt meter and see if it is charging. You should get a reading of 13.5 to 14.5 volts at the battery just off idle. (reach over the engine and operate the throttle by hand if you have a 2 valve 5.4)
Good luck.
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Joined: Apr 2010
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From: Taxachusetts
"As you probably know, the truck should run without the battery connected because the battery is only used to start the engine."
I had a brand new optima battery this summer went off road and one of the clamps sliped off the post and truck immediately died. Hooked the cable back on and it was fine.
I had a brand new optima battery this summer went off road and one of the clamps sliped off the post and truck immediately died. Hooked the cable back on and it was fine.
Last edited by bigblue61; Feb 21, 2011 at 09:01 AM. Reason: Clarification
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Posting Guru
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From: Canton, IL
BigBlue61, Use the blue QUOTE button in the lower right of each post to make sure that it is understood that you are replying to someone elses comment.
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Senior User
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From: Taxachusetts
yeah i was in a hurry and just did a quick reply with just copy and paste
