I recently installed a new alternator on my 1993 6.5 because the bearing in the old one was squealing.Shortly after (mabye a week),once in a while my battery light will come on and the guage goes down a bit.Does this day or night.I ran down the connections,and nothing jumped out at me.Guy at the parts store says to check the starter solenoid.The batteries are a year old.I'm taking a 1500 mile trip next week into the cold north,and would hate to break down on the road.If I had problems on the road,would putting a jumper from the alternator directly to the battery get me by-if in fact the alternator is not the cause?Also,if anyone has any wiring diagrams for this truck,they would be greatly appreciated.Thanks in advance.Last year when I had some engine noise,you guys were very helpful.Seems a lot of techs in my area don't know much about this engine.My truck is a 1993 chevy dually 2 wheel drive with a 5 speed manual trans and a mechanical injector pump. Thanks again, Nick

Start by putting a 15/16" wrench (or whatever size fits the nut) on the alternator pulley nut and try turning the alternator pulley. If the pulley turns and the engine doesn't, the belt is slipping! I've repaired many, many recent alternator replacement/charging problems because the belt was slipping. First thing to check.

Thanks,I have checked and all seems fine as far as the belt is concerned.Anyone know which fusible links to check?

The cable terminal connections at the battery and engine block might be loose/corroded.

Just cleaned the connections at the block,and batteries.I also replaced the spacer between the cables on the battery.Still have same trouble.

What about the grounds behind the turbo, the two braided cables, one to the frame and one to the engine. They are easlily dirty, frayed and forgotten.

Whenever I buy a used 6.5, there are four things I always do right off the bat:
1. Change filters and fluids
2. New Lift Pump
3. New OPS
4. New battery ground cables (the thickest I can find)

thanks,I didn't know there were any grounds back there.I'll get right on that one.

If your fuseable link is fried, your problem wouldn't be intermittant... :)

I had a fuseable link on my chevy gasser that wasn't fried,but when you would move it around,it made a bad connection.

Thanks for all the help.Just tooka ride in the chevy.Seems to be charging just right now.Once again,my hats off to you for taking the time to help me out. Have a Merry Christmas Nick

What was the problem?

I'm guessing it was a ground.Never did find out which one.Had my hands all aver the wiring,now it's working just fine.

Check the cable on the alternator that's for charging the batteries. It might have a fuse or something like that in it.

It's really thin anyway, best replace it with something thicker.

Had an interesting one like this yesterday. Truck would intemittently go from 13.8V to 11.x while on the road. No battery light, nada. Lights were dimmer so definitely wasn't getting the charge to the batts.

Turns out, the remarkably desgined side post bolt (+) in front of the air box was loose.

Next step - follow the thread where the good folks here recommend using the welding cables OR if I can get 'em, some slave cables from the service and rewire the primary wires...

Ah, the pain of the GM dual battery stock setup. Rather maintenance-intensive program if you remain stock...

after all my efforts of connection cleaning,and replacing a battery,it turns out my charging trouble was in fact the alternator I just installed.I guess it was the regulator.At least it had the decency to charge on my entire trip up north.Day after trip no charge.Good thing I got the lifetime guarantee model.Thanks for all the input. Nick

if you still have side terminals on batteries, get lot of corrosion under rubber and acts like resistor that may have killed alternator.