Compression Ignition Addict
Join Date: Dec 2007
Thanked 311 Times in 300 Posts
Mentioned: 8 Post(s)
Quoted: 156 Post(s)
Feedback Score: 3 reviews
The voltage actually will vary with how much "charging" is necessary. So, if your batteries were fully charged-up, then they didn't require much from the Alt and I'd say 13.4v is showing your Alternator is working. Taking it out and having it tested will show if it has the capacity to put-out the rated Amperage it has, but it's not completely "dead" now...
You said you "ran the truck for about an hour, shut it off and truck would not start". Was this at night, with the headlights/heater/radio/etc. on? Or just driving around in the daytime?
When you went to restart, did it crank-over at all? Just really slowly? Or only a few turns? Without the load of nighttime driving, I would think two, fully charged, batteries would get you a warm restart without Any help from the Alt after just an hour.