New Battery or Alternator (both)?

Jumped in the truck (2001 F150 5.4l) and it fired right up. While on the gas the battery light was coming on - let off of the gas and it went out. The needle gauge was fine. I drove it for about 6 or 7 miles then the gauge started falling also. By the time I got home, all of the electronics inside were fading or going out altogether. Good thing I was close to home.

I whipped out my battery/alternator tester. With engine off - low voltage, dead battery. With engine running, low voltage also. I bought this truck in August and the seller said the battery was replaced within the last 18 months, so I'm assuming it's alternator time.

Thoughts?

Agree on alternator. When running, it should be showing 13-14+ volts.

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Originally Posted by Irving

Agree on alternator. When running, it should be showing 13-14+ volts.

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Unless the battery has a dead cell drawing down the alternator output, or loose/corroded connection from the alternator to where it connects to charge the battery.

Jump start the truck and remove the battery + cable and see if it dies. And while it is running see if a wench will stick to the back of the alternator from the magnetic field created by the alternator.

Could be either or both, easy enough to pull both and haven them tested at an auto parts store.

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Originally Posted by SideShow Bob

Unless the battery has a dead cell drawing down the alternator output, or loose/corroded connection from the alternator to where it connects to charge the battery.

Jump start the truck and remove the battery + cable and see if it dies. And while it is running see if a wench will stick to the back of the alternator from the magnetic field created by the alternator.

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It would be the negative cable not the positive. However this is not good thing to do any longer as it could cause damage to many parts of the electrical system.

Question about alternators:
I'm not sure if my alternator is 95 amp or 110 amp. There's only a $10 difference in price. Go with the higher amp to be sure?

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Originally Posted by GilpinGuy

Question about alternators:
I'm not sure if my alternator is 95 amp or 110 amp. There's only a $10 difference in price. Go with the higher amp to be sure?

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Yes.

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Originally Posted by fportmen45

Yes.

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Is it a fair assumption that the voltage regulator/regulation circuit in ECU whatever, can manage the increased output?

In other words, is a typical "tow package" just a larger alternator and a trailer wiring circuit/harness?

Replacing the voltage regulator is usually the easy solution. Typically costs 1/4 the cost of a rebuilt one

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Originally Posted by Wulf202

Replacing the voltage regulator is usually the easy solution. Typically costs 1/4 the cost of a rebuilt one

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If you are going to take apart the alternator to replace the rectifier/regulator, you might as well replace the brushes & clean up the contact strips. Then you will have a reman alternator.

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Originally Posted by SideShow Bob

If you are going to take apart the alternator to replace the rectifier/regulator, you might as well replace the brushes & clean up the contact strips. Then you will have a reman alternator.

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you forgot the bearings.

Rebuild kits are about $15 online amazon or ebay. I try to keep one on hand for my truck.

double check for something leaking and causing a slipping belt. I had that happen with a failing power steering hose peeing on the belt/pulley.

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Originally Posted by gnihcraes

double check for something leaking and causing a slipping belt. I had that happen with a failing power steering hose peeing on the belt/pulley.

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I checked the belt and all connections including battery terminals first. All are good.

I did hook up a battery charger to the battery for a few hours and it charged right up. Then I did the old "remove the negative cable while the engine is running" and the engine cut off instantly. Appears to be the alternator, so I removed it. Kinda grinds a bit when spinning.

Now I'm searching for a place to get a Motorcraft alternator in Denver tomorrow without having to donate a kidney. I'd rather a good Motorcraft than a crappy re-manufactured one from Autozone or something. Any leads (besides the obvious stealerships)?

generator exchange - they can rebuild it or have one already done. Approximately 44th and Federal... i think they are still around. Old school repair shop.

http://generatorexchangedenver.com/

^^^^ +1 for those guys

Cool. I'll be stopping in there tomorrow. Thanks!

I'm heading out to get this alternator this morning.

So, new NAPA Electrical or re-manufactured Motorcraft from the dealership? I'm leaning Motorcraft. Same price within a few bucks.

What is the warranty on them? Personally I tend to go with Napa, but mostly because there is a store close to my house.

Same warranty. 2 years.

With napa you have the advantage of taking it back to any store

Update: NAPA New has a lifetime warranty. Done deal. In fact, installed already and running good.

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Originally Posted by GilpinGuy

Update: NAPA New has a lifetime warranty. Done deal. In fact, installed already and running good.

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If your battery is more than three years old, you might as well replace too. Be proactive instead of reactive. The frigid weather isn't over yet.

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Originally Posted by GilpinGuy

Update: NAPA New has a lifetime warranty. Done deal. In fact, installed already and running good.

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nice! Glad to hear

For whatever reason about 10 years ago, I had to replace an alternator every other week in my Xterra. 1st, Nissan under warranty, left MD stranded off road, then a Bosch, then a Napa, then Pep Boys, all remanufactured. I got so good, I could change it with my eyes closed. I got tired of trying various remans I finally got a Mean Green. Well worth the $400 premium price. After about 10 years the regulator is failing and over volting, so a new one is on the way.