So I was driving back home and had a battery warning light come on. I looked at the Edge Evo, and sure enough, the battery was at 12.1 volts. I was 100 miles away from home at the time, and I wasn't sure immediately what the problem was.

Then I noticed that the battery voltage was slowly declining. Fast forward 100 miles of stressful driving, and I pull into the driveway with dim headlights and the battery at 11.3 volts.

I connected the battery to a charger but I haven't been able to check any fuses or anything like that. Gonna do that in the morning. But I'm 99.9% sure it's not the battery since I just replaced it.

If it turns out to be a bad alternator, are there any specific ones to get or stay away from, or are most of the auto part store specials okay?

Oh yeah, don't know if it is a coincidence or anything, but my truck rolled over to 100,000 miles on the same drive. Nice way to celebrate having 100,000 miles...having a failing/dead alternator or associated components.

On a side note, thank you Odyssey for making a kick-butt battery. Don't know if I would've made it with the Die-Hard that would die every 2 weeks that I had before.

 

I agree on the Odyssey Battery, they are rock solid. With the alternator, check everything out including all grounds. Take it to a shop that can test it out. I replaced mine just for the fact I wanted a few more amps over stock. I bought one from 'American Trucks' (a sponsor here). I try not to buy a re-built anything, the Alt was a little bit pricey from American, but has been perfect so far, you get what you pay for !!

 

Start with the fuse for the alternator field, engine compartment fuse # 11.

Next check that the connector on the alternator for this is in good shape.
jbrew has a great thread on this, with pictures
https://www.f150online.com/forums/el...nator-why.html

If this tests good, next is to have the alternator removed and tested, it could be the alternator itself.

Would not be too quick to pass judgment on the diehard battery, could be you have had an alternator issue for some time. if you had run the Odyssey under the same circumstances, and it might have been dying every 2 weeks also from a lack of charge the same way.

While you are having the alternator tested, have the shop load test the battery, it could be trashed from this.

 

I checked fuse #11 (20 amp Alternator Field fuse) and it is intact and has continuity on both ends. I tried looking for the mega fuses, but I think my truck might have a different layout.



So now I'm going to check the connectors, then pull the alternator and check that out. I also removed all auxiliary equipment (lights) from the battery, and put the program back to stock on the Evo.

 

So I took the alternator out and tested the wiring that it was attached too...continuity on all ends. Took out the voltage regulator to look at the brushes, and this is what I find:





I've never taken one of these apart before, but I'm pretty sure that one brush isn't supposed to be nearly cooked while the other is nearly new.

Here is the commutator/what the brushes ride on for reference

 

Looks like the problem is found !!

 

Test resistance (Ohms) from each slip ring to the alternator case/shaft; it should be infinite (open circuit). If so, buy a set of brushes, clean the slip rings with ~200 grit sandpaper, and recheck the alternator.

 

To bring some closure to this, I replaced the alternator with a Motorcraft remanufactured unit and got the pulley swapped over to the new one. That fixed this issue. Now the battery voltage is 12.3-12.4v with the engine off, and 13.5-14.1v with the engine running.

However, now I got a CEL with codes P0171 & P0174 (system too lean bank 1 & bank 2). Oh well, gain some, lose some.

 

Check the intake to make sure the IAT and vacuum lines are all attached as before.

Usually both sides reporting this is unmetered air getting into the system that the truck cannot account for.

The leak is after the MAFS / air filter housing.

 

It's been about 6 months since I replaced the alternator, but a new issue has surfaced. Right after I replaced the alternator, I could turn on everything (blower on max, radio blasting, headlamps on, five 55w auxiliary lamps on), and the truck would maintain 13.8-14.0v. Granted, when I switched something on (like the lights, for example), the voltage would momentarily drop then jump back up to 13.8v (which I believe is normal).

However, after 6 months and about 1500 miles (truck is a weekender/spare vehicle), I noticed this morning that the battery voltage was 14.2v right after I started the truck, but it was slowly creeping down from 14.2 to 14.1 and so on. After about 10 minutes of idling, the battery was at 13.8v.

Also, when I switched everything on (headlamps, auxiliary lamps, radio, blower), the battery voltage plummeted from 13.8v to 12.9v.

It seems like the alternator isn't receiving a "signal" to crank up the output like it did before. Either that or it's just flat-out failing.

From the sounds of this thread: https://www.f150online.com/forums/el...r-problem.html it sounds like my new (remanufactured Motorcraft) alternator is bad, since I don't recall a time in the last 6 months where I haven't been able to start the truck due to a dead battery. It's almost always at 14.1-14.2v when I start it. Although I haven't noticed before if the battery voltage slowly dips while the truck is running like it is now. But on the other hand, after driving 100 miles with no alternator, I haven't driven the truck farther than the county line since I'd rather not repeat the same drive again.

I'm going to get the alternator tested (hopefully tomorrow) to see if it's actually bad or not, but any other suggestions?

 

Read this caption:

 

Thanks. I'll be sure to give that a try and report back the findings.

 

if you just replaced the alt with a stock size, then you are most likely over taxing it - alt. is only sized to the trucks stock needs, you added 25 amps just with the 5 aux light plus what ever you did not mention.

 

The alternator can handle a few extra lights if it's in good condition. 25A isn't a big deal.