That darn battery gauge went bk to low again..2 months - new wire - no issue .Had that code 2 mo ago- alternator charge low..
I had replaced entire wire from alternator to battery an the short one from battery to fuse panel..no more problems-
Today. gauges fell to low on charge an warning ..I get out disconnect cables for a few minutes ,reinstall a bit an its charging 50% now..it was 33% an falling after 1st disconnect.
I go 30 miles get home ,still at 50% on charge [ good level] an turn it off,then I restart an again battery gauge is on 33% again..[ anytime it's that low it will go down with this problem]
Is this likely a wire issue again or that darn voltage regulator in the pcm?.
I'm leaning more to wires at battery , but after disconnect of battery that may reset pcm to start again at 50% -on charge gauge 'before pcm relearn ..
-any info is appreciated.

 

Did you ever replace the alternator?

What is actual running/charging voltage at the PDC?

 

Yes 2 mo ago an both tested good off truck . Do these type slowly start not charging a little at a time as they fail or is it usually a good charge or no charge .
I need to retest it again today . After resecuring cables an connections

 

Alternators have a variety of failure modes, but, generally, unless you own the truck for a LONG time, you will only replace it once..... Voltage regulators are pretty much the same way. More often than not though, they either work, or they don't. It's possible something is getting hot, and then slowly failing, The fun part is, figuring out which part is actually failing, but NOT by replacing them.

In this day and age of everything outsourced to third world countries, the quality of replacement parts has declined dramatically. They try and convince us that these parts are 'just as good' as USA made parts, but, in my experience, that is most certainly NOT the case. And that applies to darn near EVERYTHING.... not just auto parts.

 

The Altenator is a stand alone power supply, and regulates his own voltage output, so the PCM only recieves what it's getting from the altenator.

Did you measure the volts at the battery with a multimeter ? with engine off should read 12 volts and with engine running and altenator charging it should read about 14 Volts, you might have to rev it up some to 1000 RPM's.

If you get the right readings you have to search if the PCM get's a good voltage in and out to the dash, you should need wiring diagrams to test and measure the charging system, PCM and voltage meter on the dash.

Looks to me there's a bad connection or a short in the wiring in the PDC somewere.

 

This is crazy..left cables off a while ,restart an its14.1 a while an no change ..I turn off. An 10 sec later 11.5 an dropping ....I did reconnect an still low...I tap alt a tiny bit an restart bk to charging...I can go forever then ..but after turn off an restart -b k down ..

diode? What's next ..if alternator is bad it wont read 14. An stay up high .

 

If you only touched the altenator, it seems to me there's something wrong with the altenator it self, like you said a diode on the internal voltage regulator most likely.

On the other hand, because you have a new altenator and had it tested outside the car.
You know for sure you're wiring is all good ?, i assume the power side is good as you changed them already.
Meaning you know for sure you have decent GROUND.
If you have bad or corroded grounds on the chassis, engine and so on you could have strange things to happen.
I would loosen up and clean all the ground points to start with.

 

Pull the alternator and go get it tested. Don't have it tested while in the truck.

 

Might be gunk in connector at alternator to ecm. ..Not sure ,but I lubricated the heck outta the connections an the 2 wire especially. Also hit the alternator some an sprayed the copper down too...rechecked ground .
so far now after 2nd an 3rd restart it stays at normal 13.9 or 14..
I'm thinking that small connector may have had connection issues .
What all does hitting it do ,? Still surprised how such a light tap impacted voltage..but that can impact the 2 wires I'm sure ..
Also what should voltage be at that connector ?

 

FWIW, when i changed the cooling system on my truck, I found that the accessory bracket was arcing to the intake manifold under the AC compressor - everything is powdercoated and the unmistakable lightning bolt marks were present in both, down to bare metal. Definitely not a rub. So I added a ground wire to the bottom alternator bolt.