-1990 F250 5.8 2wd)
I think my alternator might be bad. hopped in truck yesterday drove to kid's school, started again, drove to bank, started but seemed to kind of a slow crank before it fired. Went to grocery store, came out of grocery store and it tried to crank and then wouldn't again, like dead battery. I got a jump at the grocery store and drove it home.

I put it on a charger overnight, woke up and after removing charger it started right up. So I let it sit for an hour, came back and tried again, sure enough it started fine. Took my kids to the park an hour later and after playing at park for a while it started up fine again.
At this point I drove kid to school, went to a drive thru, took a small drive around town and during this trip never turned off the truck. I had the radio on but no heater , no lights cuz I suspected the alternator may be bad and didn't want to be draining the battery faster. As I headed home I noticed the turn signal was blinking much slower, and I thought that since I had driven around for a while with radio on.. at this point battery with no charge from alternator might be getting low. pulled into driveway at home, killed engine, waited about 10 seconds and then tried to start truck again. Acts like dead battery again.

While driving the meter has it down just above the red section labeled 8 so I am guessing it's got maybe 10 volts at that point. a few weeks ago the meter would always read right in the middle, about where the 13 or 14 volt mark would be with the noticeable drops happening if I cranked heater / lights etc.

Do you think my diagnosis of the bad alternator is correct or has anyone run into a similar problem and found it to be something else? I know an old chevy I had I thought had a bad alternator once and turned out to be a problem with the voltage regulator.

I've been reading up on the forums and the general consensus seems to be to upgrade to a "3g" alternator rather than the stock replacement parts as well.

If any of you can provide your feedback or experiences I greatly appreciate it. Thanks in advance!

 

Sounds like a dead alternator to me, and yes I would upgrade to a 3G as well. I installed one in my old '69 F250, and it was very easy.

To test your current alt get the truck running and measure the voltage across the battery terminals. If you see anything less than 13 volts your alternator isn't working. This assumes no damaged wiring or burned fuse links.

 

Its funny because im dealing with the same symptoms as you are. Pretty sure its a bad alternator as well. Go with 3g alt. Thats what im doin

 

Got a "new" alternator , installed, everything running great again.