In my opinion,(which has been worth squat lately) you my friend, have a bad alt or a bad pig tail to the alt. Happened on my Excursion.

 

Remember that at cold start, your running the highest demand of the system, glow plugs, FICM and various other things.

As the system nears a fully charged state, the demand will decrease. The heat is from resistance, not necessarily from working hard.

 

Not sure if I can test the pigtail. So I guess taking the alternator to a local parts store to check if it is good will determine if it is the pigtail or alternator? Not sure if I can find another pigtail to test to see if it is functioning or not. Maybe I can check DCPower to see if they sell replacement pigtails.

 

Someday I finish my videos, but without being it sure looks like a bad alternator or pigtail. Even if you had nothing but stock cables, which by the way the stock cables will handle a 190a but with a few tenths voltage drop at max output, with that 190a alternator you should never be below 13.6v. Everything you just mentioned about how your truck ran due to voltage swings says alternator or the push to connect plug.

The push to connect plug has two wires, one that goes to the dash panel to set off the battery light if the alternator is not supplying voltage higher then the battery voltage (this never should been a battery icon, it should be an alternator icon) and the sense wire that loops back to the main splice for alternator output, glow plugs, and battery. Some people have had issues with the pigtail connector at the alternator from not fulling plugging it in, or with the installation of a new alternator mishandle the wire or place it in a stressed position.

If the alternator is a sometime work, sometimes not, having it checked at the store can be hit or miss unfortunately. There are two things you could try. When the alternator is not generating, playing with the connector and pigtail and getting it to supply voltage would be a check. The second is a farm-boy check.

If the brushes are hanging in the holder and preventing alternator output, light raps with a small object, like a screwdriver handle, could free the brush for a short time. Works on the farm, but not a professional mechanic resolution. But I told that to an engineer who was freaking out half way between Dulles and his home in Va and it got him home. It's a backyard check, you just don't want to screw up a warranty if there still is one.

 

I'd re-read post #5 as Tedster suggests, checking the charge at both the batteries and the alternator terminal, checking both static and running at a variety of rpm's. Also wait a few minutes after running and do it again.

Alternator brushes can get old and worn and after the alternator warms up a bit, stop charging. I've had it happen on both alternators and fuel pumps.

I've seen regulator diodes burn out if jumping another person's battery while your engine is running. Maybe something you've done recently?

 

Yeah, I will have to check with my voltmeter to see what is going on. The alternator is about 6 months old and has probably less than 1000 miles on it, so hopefully the brushes aren't worn out yet. Haven't jumped started anyone with my truck yet, so if won't be that.

 

Just because it's new does not mean that its functioning correctly... the only correct answer is to verify it's functionality. Anything can happen/will happen when you least expect it to happen.... even expensive ones break early and often.

My batteries are at 12.65 and on a cold start, FICM sees 10.5v for a second with glow plugs on. Yours is at 11.6v and see's 9.6v for a second.. your that close to 9.0v and toast.

Get it checked, get it checked now... before it's costs you more in the long run (FICMs are $$$$... notice I put 4 $$$$ to indicate BIG money)! When that bad boy hits 9.0V for input power to the logic circuit... it's done.

 

When I bought a reconditioned alternator at Kragen for my Expy, now OReily's, my first forever warranty unit lasted about 30k. I then had to get a replacement and it started to hum with a bad bearing after 5k. Replaced that unit for almost 30k and it also went bad.

So much for a forever type product but glad the replacement was a 30 minute job.

Last summer when visiting up in Bemidji, MN, getting some parts at their OReilly's, an F-250 came in and needEd to exchange his forever unit too. Not just me.

Anything is possible to Randy's point.

 

I had to rep you for that post, Bob, seeing as we have very similar vehicles. I too replaced a Kragen "lifetime" and "new" alternator, and then the nice guys at O'Reilly's gave me their New Lifetime unit -- nice was that is was rated at higher amps.

We'll see how long this one lasts....

 

Thanks DD?
Nothing like a big pat on the back!
Always appreciate your posts and comments,

 

Sorry for the late update (sorta update). Well first after letting the truck sit for a little over a week since the full charge drive to and from work I found that the Voltage was 12.3. I put the charger on and it didn't take that long to get it fully charged. Maybe a couple hours at 10 amps. Before it took many many hours to get sorta charged, so not sure how accurate the 12.3 volt was. Anyway while under the hood I was checking the connections and everything looked good. I went to pull on the pigtail adapter and it pulled right off the connector. So I pushed it back in until I heard it click. Now it won't come off unless I pull the tab back. So that could have been the problem, the connection may have been just barely touching. I haven't driven the truck since I found this this past Saturday, so I'll update how everything goes once I take it out.

 

Well looks like the simplest solution was the correct one. Finally was able to drive the truck today and voltage went right to 14.4 volts and slowly came down to 13.9 after an hour of driving. No more wild fluctuations of voltage from 11.8-14.6. So thanks for the idea on checking the pigtail. Saved a lot of time since I didn't have to take anything apart.

 

No problem,that is what we are here for.