I apologize for not replying earlier when you're willing to help me out. I wasn't able to get to the truck until today but this is what I came up with:

Prior to start: 12.28V
Ignition on, glow plugs cycling, engine not running: 11.4 V
At startup: 12.23V
After 120 seconds: 13.09 - 13.20
After 15 min all off: 12.85
After an 18 mi drive, all on: 12.85V
After an 18 mi drive, all off: 12.75V
Turned off: 12.59V

All readings were taken at the passenger's side battery. My Insight is showing about .4V lower than what I'm getting with the multi-meter at the battery. Today I saw 46.5 on my Insight for my FICM V for the first time. Most of the time it was fluctuating between 47-48, but today it would occasionally drop to 46.5, which I have never seen before.

Thanks!

 

Delays not a problem. I'm the poster child of life getting in the way.


"All readings were taken at the passenger's side battery"

Prior to start: 12.28V. Too Low, should be a min of 12.5-12.6v
Ignition on, glow plugs cycling, engine not running: 11.4 V. OK
At startup: 12.23V. Not bad
After 120 seconds: 13.09 - 13.20. Low
After 15 min all off: 12.85 Low
After an 18 mi drive, all on: 12.85V. Low
After an 18 mi drive, all off: 12.75V. Low
Turned off: 12.59V. Should be over 13v on initial off until the surface change is dissipated.

Here is a graph of how my 140a Bosch alternator did when I tested it. This with the small pulley should have an output just slightly lower then yours if you have a stock sized pulley. I never had the DC alternator in my hands and I've had conflicting data if its stock or undersize from the box. Voltage is taken at the pass battery.




I lost my post warmup data in iCloud and need to redo that, so my comments are from observation not data based.Just because everything is consistently low, have you checked the voltmeter against another source?

 

I just tested the voltmeter on my '04 Durango with a 3500 alternator and it was at 14.8 V at idle.

According to the paperwork I got back from DC Power when they sent the alternator back after repair my pulley size is 2.22 inches. I measured the pulley before I bothered to look at the paper (duh) and it is approximately 2 3/16" across. It was kinda hard to get an exact measurement with the fan shroud in the way.

I read a suggestion that I take the pigtail off the alternator and measure the V at the #3 pin and that the V at the #3 pin, the alternator post and the batteries + posts should all be within .5 V of each other. I am apprehensive to disconnect the pigtail with the engine running as I'm not sure what the second wire does and I don't want to break more stuff.

According to the paperwork from DC power the alternator was putting out 14V and 54 amps at 1600 alternator RPMs and 190 at 10,000 alternator RPMS.

I'm at a loss as my electrical system is doing the same thing it was before I sent this alternator in for repair....ugh.

 

There is no reason to have the engine running while pulling the controlling connector and checking them. But to throw this out, you never remove the cable from the main power post when the engine is running.

I’ve got a vid on YouTube about the battery light coming on, not the issue you have, but I go over testing the small connector circuits. The sense wire should be reading exactly where the battery voltage is at, key off, key on. It’s always connected to the battery positive. It's what tells the alternator how much to output, if voltage is too low. It would be a good thing to check, but I don't know DC's circuit architecture for control, but I have a hard time understanding how a lower voltage at the sense wire would not cause a higher generated output, the opposite.

There is something goofy here that I'm not understanding.

 

So I checked the V at both batteries, the alternator post and the sensing wire and all are at 12.37V. I would like to believe that DC Power didn't just send the alternator back without repairing, and I'm not saying that's the case, it but I don't know what else would be causing this.

 

I wouldn't rule it out. I had mine repaired this summer and it showed up without the pulley that Anthony said he would include. I hate to bash on forums as I spend time here for info (and if I have it to provide it) but heavens to murgatroyd the back housing on the casing was clocked wrong. While bolting up the housing was twisting when tightening down to the bracket. This caused the alternator to not spin freely. Obviously something was wrong. Took the alternator off and noticed the mounting tabs were not flush with each other. Re-clocked the alternator so that it would bolt up correctly. I checked with DCpower and they offered to send out a shipping label to send it back but after waiting 6 weeks for the repair I figured if it spun freely it would be ok.


Before someone chimes in about a Leece Neville I did send an inquiry to FicmRepair but never got a reply so just re-installed it and voltage is good.

 

Well that's great news!!! After spending what I spent on the alternator itself, then spending $30+ dollars to ship it back to DC Power, then another $61.00 for repairs and to have it shipped back I'm not going to be happy if I have it bench tested and it's still not putting out the proper voltage. They sent a piece of paper showing that it was putting out 14V so I don't know why it would suddenly stop doing so.

WIth the amount of money I've spent to get it this truck running and to keep it running this is getting old, not to mention that I have a travel trailer I'm making payments on that I can't use. Ok, done complaining for the day.

 

Are you checking the batteries isolated or with all the cables connected. Again, the vid shows the simple way to check. Your saying both batteries are exactly the same, but they won’t be disconnected.

 

Everything was connected. I just found your video and will try the steps when I get back from Napa. My thanks again.

 

So I checked it with the batteries separated before I went to Napa as it would bother me the whole time. Passenger's side was at 12.44V and driver's side was at 12.45V. I don't have a battery tester.

 

So by voltage they are low, either not fully charged up or internally deficient. I realize you had them tested, but did you get a current capacity ability? This may not be the issue but just trying to close open ends.

 

So I just had the batteries tested again and the passenger's side was at 1000+/850 and the driver's side was at 950+/850, I forget the exact #s. They tested the V and it bounced between 12.1 - 12.3 at idle. When I first started the truck after glow plugs cycled the Vs were between 13.1 - 13.3, but as everything started warming up you could see the Vs starting to drop. I'm going to call DC Power and see what they have to say. The last thing I want to do is fork out $ for two new batteries or to have my FICM repaired again. I would think that if it was a ground issue they wouldn't be at 13.1 - 13.3 at startup after the glow plugs cycle.

 

You don’t have a battery capacity issue, they are at good value for the temp, just low in voltage and need to be charged. I would put a charger on those batts and bring them up. Even better if you have time hook up a maintenance charger if you have one. I’ve been amazed how much higher and stable batteries are when they occasionally get fed by just under an amp for a few days.

I too also think it’s leaning like an alternator issue. But to get ducks in a row you should check the back connector, engine not running.

 

Will do on the charger, thanks. Excuse my ignorance but what is a "back connector"? Is that the second wire in the pigtail that controls the battery light.

Just to make my vehicle issues that much better my Durango just stopped running today as we were coming home from taking the kiddos to get pumpkins...life's good.

 

Wait until your body starts doing all this crap ....

Yep, I meant the connector with two wires in the back, voltage sense and tigger/lamp.