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Old 08-12-2017, 11:05 PM   #1
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Default Alternator Amps

Does anybody know how to tell what amp alternator I have in my 2004 F150 Lariat 4x4 with 5.4L? I got a P0622 Generator Field "F" Control Circuit Malfunction while driving home. My reading from my Torque Pro app showed voltage only at 11.4 volts. When I got home and checked the battery voltage with the truck off, it was 12.16 volts. I put a new battery in last year so it should be good. As soon as I start it, the voltage drops back down into the 11's. I'm assuming my alternator is bad and need to know what amp alternator to replace it with. Any ideas? Thanks.
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Old 08-13-2017, 03:03 AM   #2
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I'd use a multi meter and test at the battery.

Your volts are low on your battery. Should be a minimum of 12.4 with the truck off, 12.6 is good. Could be the alternator is not adequately charging the battery if it's only a year old.

So, check the voltage at the battery with the truck off, then start the truck. At idle, you should get a minimum of 13.4-5 Volts. 13.6 is good. Then, rev the engine to about 15-1700 rpm's, should see an increase to around 14V.

Any less than mentioned will cause malfunctions. Seen it many times, and happened to mine couple of years ago. If the alternator is working, just not enough output, then most times, it's the brushes wearing down and no longer generating adequately.

If this is the case, you can replace the brushes for around $7. Easy fix, DIY youtube videos available. If you replace the unit, make SURE to use OEM. No aftermarket. They cause crazy issues as these trucks are very picky.

I would advise to check this asap and repair if this is the issue asap. Reason is, there is a certain voltage (still don't know the exact number and this happened to me) that when dropped to, the truck will lose all power, just die. Did it to me on I-85 running 75mph with a tandem axle covered trailer in tow. Bad thing is, this cuts vacuum to the IWE's and your hubs engage....or try to, and can damage them as well. Has happened to many others as well.

Also, if your readings at idle come out borderline, turn the A/C on wide open, radio on, seat heater if applicable, wipers, head/fog lights. You should still be able to maintain same voltage with additional draw.

The additional draw from the lights on my covered trailer is what I believe triggered my failure/shut down. Battery was 6 months old, no warning, no prior issues. Lesson learned.

Hope this helps.
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Old 08-13-2017, 07:42 AM   #3
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Thanks. I'm sure the volts are low on the battery reading cause the check charging system came on a few miles from home indicating that my alternator wasn't charging. As I said, when I checked the voltage at the battery with the truck idling, it was only in the 11's so the alternator isn't charging. I need to know what amp and which alternator to get. My window sticker says 130 amp but rock auto doesn't list a 130 amp for my truck... only 95, 110, and 115. I want to get a Motorcraft one but have read bad things about remanufactured Motorcraft alternators which they all are now. I would like to know a part number of what Motorcraft alternator to get. The pictures on rock auto look like mine is the 110 amp version but I want what is supposed to be in mine, not necessarily what's currently in it. I don't know if somebody has put the wrong one in over the years.

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Old 08-13-2017, 10:32 AM   #4
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Get the 110 amp motorcraft re-man..
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Old 08-13-2017, 12:09 PM   #5
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Default Get the 110-amp motorcraft reman

I have a 2004 XLT with the 5.4

A year or so ago, my dash light came on and I decided thatit was probably my alternator.

So I went to the official ford parts website and they hadtwo options. They had a 110 amp optionand a 130 amp option.

My window sticker (which I still have) clearly says “130 amp alternator”

So I went to my dealer (didn’t order it from the website)and asked them. They said the only option for my truck is a 110-amp reman from motorcraft.

I showed them my window sticker and I showed them the ford parts website (remember this is the actual ford parts website.. not someone else).

The dealer parts guys were curious. They called ford. Ford says use the 110 amp. At this point, I could have gone two ways. I knew if I got the 110 I would wonder, so I rolled the dice and got the 130 amp motorcraft reman.

It fit fine and the voltage was fine. But the red “battery” dash light was on andstayed on. Something was wrong.

I took it to autozone to have them check it. Their meter said the voltage regulator was bad.

So I went back to the dealer parts department and they were very cool. They gave me another motorcraft reman 130-amp alternator.

Same thing. The voltage was fine but the dash light stayed on. I took it to autozone and the charging system checked out fine.

The connector on the wire to the alternator was cracked, soI changed the wire harness from the alternator to the battery (although the crack was small and seemed unlikely to matter).

Nothing changed. The dash light stayed on and the voltage was fine.

So I went back to the dealer and got the 110 amp motorcraft reman. (which I had to buy... not complaining tho)

And that did it. The voltage was fine and the dash light was not on.

I don’t mind working on my truck like this. I knew I was going out on a limb and it didn’twork. Nothing ventured, nothing gained.

Interestingly, the 130 amp option is now gone from the ford parts website and it only list the 110.

I heartily recommend that you get the 110-amp motorcraft reman.
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Old 08-13-2017, 12:28 PM   #6
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Thanks for the info. Rock Auto lists 2 different Motorcraft 110 amp alternators and 2 different 115 amp alternators for my truck all remanufactured. I have no idea which one to get. I'm going to pull mine off and see if I can find a number on it. I have no idea what previous owners may have put on it though. Why do they have so many listed even within the Motorcraft brand? I've gone to fordparts.com and gotten a number and another ford dealer's website and gotten a different number, both using my VIN. I'm not sure why the different numbers and multiple options. Sure makes it hard to pick one.
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Old 08-13-2017, 01:21 PM   #7
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I told you.. get the 110 amp motorcraft re-man.. but , again it's your truck.
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Old 08-13-2017, 02:06 PM   #8
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There's more than one model of 110 amp Motorcraft remanufactured alternator to choose from all with different part numbers. Each site with Ford parts I go to gives me a different number. What's the difference between. them all and why do they all say they fit my truck? I'm not arguing with your 110 amp recommendation just don't know which one to get.
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Old 08-13-2017, 02:24 PM   #9
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Have you compared the 2's pics to yours?

Add on: I only see one at the bottom of the page, the item up top appears to be a starter.



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Old 08-13-2017, 02:27 PM   #10
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One has a pic and one doesn't. The one that has a pic is much more expensive. Imagine that... lol.
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