npccpartsman and I both brought up a question about alt charging and the charge status of the batteries in the so what did you do today thread. Well normally when I start the truck it's does the normal drop then after the gp cycle it will jump up to 14.1 and while driving will stay there for a few miles then drop to 13.5 to 13.8 (depending on what I have turned on) leading me to believe that after that amount of time the batteries are topped off and the alt. doesn't need to put out as much (no real charge to batteries needed)
The last two days my alt volts have stayed from 14 to 14.2 the entire drive to work and home. Does this mean my batteries are going south?

 

Has it by chance been colder there lately? Lower temperature means higher internal resistance of a battery. That means a higher charging voltage to overcome this.

 

Probably some additional load is being drawn. Load test each battery seperately to establish a baseline. Then while watching vlts un plug one circuit at a time see if anything changes. Voltage draw down test. Work upstream from there.

 

Voltage regulator has a set voltage and should remain at that or near that voltage at all times.

If the voltage is dropping after a period of time likely the alternator is getting hot and the output is weak.

The alternator's job is to power the electrical system, not charge the battery.

Josh

 

So basicaly the old unplug the batts and see if it will still run off of alt will still work?

 

Ok--makes sense. It has been colder the last couple of days but has been this cold previous and didn't notice the 14 volt staying up. It has always (since I bought the truck) Dropped to the 13.5 to 13.8 after ~the same amount of time operating. So it's nothing to do with the batteries at all just the load needed from the alt and the v. regulator and whether it's weak or not--should be constant--did I get that right?

 

Sure, if you want to chance frying the PCM and FICM

Sort of works on a point ignition system. Computer controlled not so much.

Josh

 

Should be a fairly constant voltage.

If voltage is dropping after some amount of driving the alternator is getting hot.

Josh

 

Thanks for clarifying that. That was the main reason I never tried it on a modern engine.
Bad things could/would happen. LOL The old point systems it was no biggie. Used to be the most common field test if you had no testers on hand.

 

Got it. On the way home from work it bounced from 13.6 to 14.0 barely staying on one for very long (maybe a few seconds)
Now my dumb question--because I have no clue--how in the world can this thing get hot like that over a year (minimum) and not be fried? Is it design and the up and down from the regulator keeps it safe? Again green horn questions as I have never had to pay attention to volts until I got the 6.0.

2006 F350 4X4

 

Your alternator is good. Start worrying about it when you see less than 13 volts or more than 15 volts when running. As for your batteries, (assuming a post guru has a SGII) watch your volts on the sgII when you shut off your truck. It should hang out at 12.6 (100% battery life)

 

Sg???


Just kidding yes I have sg and torque pro. Koeo batteries always at 12.6--so far.

2006 F350 4X4

 

haha I was about to say 'WHAT?!'

 

ya youre good. my voltage fluctuates just like yours too

 

you can also check for any AC Mili volts at the output of the alternator. It shouldn't put out any AC voltage. If it does then a diode or two are going bad. The diodes are what rectify the AC current the alternator makes to DC. Batteries create DC current/ Alternator makes AC current then get rectified to DC