Alternator problems(I think)
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FTE Chapter Leader
Joined: May 2006
Posts: 11,273
Likes: 100
From: North Dakota
Alternator problems(I think)
Well, my voltage has always dropped at idle,at a stop light,with the lights and blower motor on. Well the alt has been making alot of noise, so I replace it.. So today, I notice my voltage gauge reads lower than it use to, so after a 15 mile drive on the hwy home, (After stopping by the parts store to have them test the battery and alternator both test good) I pulled out my multi meter and tested it for myself... Here is what I got,
battery voltage with vehicle OFF 12.55 volts
running with everything shut off, at idle 13.85 volts
put into D at idle, 13.85 - 13.90 volts
turned on headlights and A/C on high, in D at idle 12.41-12.54 volts
Now, I turned lights and A/C off, ran motor at about 2500 rpm for almost one min. and the voltage struggled to reach 14 volts...
Is this normal? I'm thinking NO, I was almost positive that my other vehicles ran at 13.5-14.75 volts all the time when running.. and YES the battery cables and all connections are good and clean..
The guy at the paarts store said it was pushing 36 amps at idle, and the voltage was within spec...
battery voltage with vehicle OFF 12.55 volts
running with everything shut off, at idle 13.85 volts
put into D at idle, 13.85 - 13.90 volts
turned on headlights and A/C on high, in D at idle 12.41-12.54 volts
Now, I turned lights and A/C off, ran motor at about 2500 rpm for almost one min. and the voltage struggled to reach 14 volts...
Is this normal? I'm thinking NO, I was almost positive that my other vehicles ran at 13.5-14.75 volts all the time when running.. and YES the battery cables and all connections are good and clean..
The guy at the paarts store said it was pushing 36 amps at idle, and the voltage was within spec...
Thread Starter
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FTE Chapter Leader
Joined: May 2006
Posts: 11,273
Likes: 100
From: North Dakota
Impossible that the belt is slipping, it has a new belt, and tentioner. I was looking at the spEcs in my repair manual, and it said, at 1000 rpms, it should be .5 -2.5 volts more than when its shut off, so I guess according to that, its within spec. But I've never had a ford have so much voltage drop at idle on a stock rig. I could understand it if I had abunch of lights on it. But o well.
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Elder User
Joined: Jun 2010
Posts: 641
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From: TX
Oh okay. Maybe it's just a little pooched up but yeah oh well :/ It's "tensioner" BTW 
Mine reads at a steady 14.0V Something just came to me. Maybe the voltage regulator on the alternator is bad. That must be the problem if the alternator itself is still good. Please a REP point if I am correct.
Mine reads at a steady 14.0V Something just came to me. Maybe the voltage regulator on the alternator is bad. That must be the problem if the alternator itself is still good. Please a REP point if I am correct.
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Thread Starter
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FTE Chapter Leader
Joined: May 2006
Posts: 11,273
Likes: 100
From: North Dakota
Never been much of a good speller. Lol. But 9 times out of 10 when a regulator goEs bad, it kicks out too much voltage. Maybe I'll have to find one of those "old timer" alternator testers and see what it comes up with.
Elder User
Joined: Jun 2010
Posts: 641
Likes: 0
From: TX
If there's voltage drop, it's either a bad wire between the alternator and battery, a bad alternator, or a bad voltage regulator. Nothing else it could be. Go test it again. Have to keep in mind that when they are tested they have minor load.
