I have a 2002 Excursion 7.3. The truck has recently started eating alternators. I've gone thru 4 in the last 7 months. I put a new one on Saturday and already getting a no charge situation. I'm not opposed to the idea the Chines made stuff from Napa is simply crap, but the one that failed Saturday was American made from Nations Starters & Alternators and was just put on in December.

Is there something electrical that can be chewing up alternators?

 

A battery with an internally shorted cell or two.
A bad engine block to body to battery ground path.
Excessive battery discharging and recharging.

 

Is there a chance you can find out what exactly is failing in the alternator? The regulator? The diodes?

 

OK, I made it home yesterday. I originally posted from my phone after driving 42 miles to my job site. The charging system warning light was on and my in-truck voltmeter was displaying 12.0 volts. After sitting about 4 hours, I started the truck and voltage displayed 13.3 so I drove away. On the way home the voltage slowly increased to 13.9 - same as it showed Saturday afternoon when newly installed.

When I got home I did a quick test - with the engine off, I disconnected each battery in turn while checking the other with my mutimeter. I read 12.69 volts on each battery, and about 12.2 with the lights on.

I went out this morning and did the same test and read 12.48 across each battery and about 11.95 with the lights on.

I know enough about the electrical system that the results from yesterday afternoon are normal, but what of this morning? Clearly, there is some drain going on, but is this normal? If not, is this enough to fry the alternator? And if it is enough to fry the alternator, will it do it in 2 days and less than 150 miles of driving?


When they've failed, all I've done is go back to NAPA and have them run their test to verify failure. I've never asked what failed and don't know if they can tell.

 

Some of those machines will tell them what is wrong.

Your voltage was low in the morning. Did it crank over ok or a little slow? We don't know if the voltage was low because the batteries were really low, or because the alternator was not charging at all. If the batteries were really low, you should have noticed it cranking over slowly, and after it did start, that would put a tremendous load on the alternator and pull the voltage down like that. After driving it for a little while the voltage on your dash gauge should slowly make it's way back up as the batteries took charge.

If it cranked over fine, but the voltage was low like that, then we can assume the alternator was not working at that time. But if it works later on, we can assume it may be good and you have another problem.