Alright so my issue is that my battery light and "check charging system" message appear when I go for a drive. I took the truck to both Autozone and O'Reilly's but they said the alternator and battery were fine. The battery is a Duralast Gold and was purchased 12/2016 so it's less than 6 months old. When the truck is running it is putting out 14.4V so that's why the alternator is checking out. I had the truck into the dealership a couple weeks ago and they said the wiring harness for the alternator needed to be replaced. Well... after waiting 12 days for the part I finally installed it and my problem is not fixed. I was driving down the highway and the light came on so I headed towards the next exit and I reduced the fan speed for the air conditioning system and the light went away. This made me think that the load was too much for the alternator to handle and that's why the light came on. I got back on the highway heading back home and the light came on again. I turned the a/c off but the light stayed on. I slowed down and the light went off.
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Do you think it could be the voltage regulator?
Do you think I should replace the alternator?

The dealership website lists these:

The Ford retail spec is GLV-8704-RM costs $192.42
The dealer part new (replaced by re-manufacture) is GL-922 and costs $292.45
The re-manufactured part is GL-974-RM and costs $292.45

I've been told to stick with original equipment and so far this is the best deal I could find. It is a re-manufactured motorcraft alternator (part GL-974-RM) for $130 on Ebay. This is $160 less than the dealer for the same exact part!

Thoughts?


http://www.ebay.com/itm/MOTORCRAFT-F...3D302260425842

 

That would be my route if I thought I needed an alternator. I too hear these trucks are picky about their alternators, stick with oem

 

Definitely the voltage regulator in that alt.. our trucks are very picky about that.. get the motorcraft re-reman.. problems solved

 

The regulator on these alt have brushes that contact the two rings of the rotor . The rotor is where the ac volts is picked up ,the voltage reg converts this to dc thru rectifiers and charges battery . The voltage reg controls the stator field to get ac off rotor . The old generators had brushes too but it had a commutator with segments to sort it out to dc, no rectifiers .
Sounds to me that your brushes are making intermittent contact or volt regulator going bad . Probably why it tests good sometimes . These reman outfits do the very minimum to get their product out the door cheap. No expertise at all .
Just had a go round with sears auto for a friend ,her two batteries were in warranty but they would not honor it on her diesel truck with new alternator . We bought the new ones and that fixed it . Their machine must lean towards not replacing . I should have spiked them with baking soda . We did have to charge them up to get there .

 

Mine was doing something similar.. the output appeared to be okay occasionally, but then I'd check and it'd be sitting at 11.X V while running.


Replaced with a reman duralast that came with a lifetime warranty for like 200ish bucks. Bingo.

 

I removed the alternator and now I'm waiting for a ride to Autozone to see how it tests on the bench. I looked at a couple videos and forums about the alternator and it seems like replacing the brushes and voltage regulator would be pretty simple. I don't want to take it apart until after I have it checked on the bench though. Also I think buying a new or reman alternator would be easier. I couldn't find what type of alternator this is but it looks like the motorcraft one.

 

I had my alternator die while out on a trail, took it to O'Reillys, tested and replaced it. In the past 6 months since I originally replaced it, I've had to replace it 3 more times. 1 wouldn't produce charge and caused the check charging system error, 2 had faulty bearings. Seems to be a problem on these model years. Get one with a lifetime warranty.

 

Seems to be a problem with an aftermarket alternator. Go with OEM rebuilt.

 

that alternator has a PCM-controlled regulator, the voltage set-point is controlled by the computer and can be anywhere from 12.5v to 15.5v during normal operation, depending on what charging mode the system is in.

The most common failure point on these alts is the brushes and the slip rings - the OEM Motorcraft regs themselves almost never fail, but because the brushes are built into them and designed to be non-serviceable, you have to replace the entire regulator when the brushes get too short to have full contact with the slip rings. Replacing the regulator isn't impossible but Ford made it a hassle - the tolerance ring holding the rear bearing is not designed to be easily removed and breaks easily upon removal - and getting the regulator out without breaking the brushes is tough too. The regulator screws have to be properly torqued down or the replacement reg will fail in short order. You should always replace that rear bearing and tolerance ring if you open the alternator. If your slip rings are bad you are better off not messing with it and just get a complete alternator - the replacement leads have to be spot welded and epoxied in or they will fly apart at highway rpms. That is the easiest way to tell if you have a poor rebuild job.

The best way to tell if the alternator is going bad on an intermittent charging issue is to just tap the thick part of the case near the plugin while it is not charging- if it kicks on you know it is probably the brushes making contact again. The plug-in harnesses are known for going bad too - jiggle the plug or press in on the wires and see if it affects the charging.

One of the main reasons these can be so picky is that Ford has made three running changes on that PCM regulator; they are usually backwards-compatible, but if you use the wrong one (or a non-pcm reg - they look identical but have a different color case) you got problems, and aftermarket regulators may not be able to exactly copy all the functions of the OEM electronics, they might work but if the PCM doesn't like the signal it will turn the light on. If you can't get an OEM Motorcraft VP4L3U-10C359-AA reg I would recommend the Taditel T902.

If that sounds intimidating, go with the Motorcraft reman alt - just check the warranty terms before you order it online.

 

Well I just got back from O'Reilly's and the alternator passed! The guy said he checked it 4 times to be sure and said he didn't feel comfortable selling me a replacement because if it didn't fix the problem I couldn't return it. He said it was putting out 14.5V and had a max of like 15V or 15.X V which he said was within normal range. He mentioned the bearings or okay at best and you can hear a little bit of squeaking (this may be my issue). I also noticed the belt was cracking and also "okay" at best. I'm thinking about replacing the belt and I may eventually replace the alternator when I can afford it but for now I think I will continue driving the truck and see if my battery dies. I may also go back to the dealership to see what they find.