starting/charging issue

[snowmobiler7c]

I have a 03 7.3L truck. I just replaced one battery last month under warranty and having starting issues. I wanted to replace both but since the one tested good they would not replace them both at the same time.

The last few days the truck seemed to crank slow but start and run normal. Then yesterday i ran the truck for about an hour, shut it off and truck would not start. I jumped it got it home and let it sit now no power at all to the truck. Batteries are completely drained. Batteries were charged and both tested good today at sears. When the truck is running im having no issues what so ever. I would think with an alternator issue the guages and headlights would be dimming.

Is there anything else besides a short that could be an issue? Anyway to check the alternator while still on the truck? I havent looked but beleive the 7.3L had two alternators???

[NoRalPh]

Some had two (not many, it was an option) and the test for whether the Alt is putting anything out or not starts with a VoltMeter. Monitor your voltage, it should be 13.5+ when running (not for the first 2mins or so though as it's shut-down when the Glow Plugs are on).

If the Batteries are good, you're either not recharging them back up from the Alternator or they're being drawn-down because you have an electrical load you shouldn't as it sits (often called a "parasitic draw")

[snowmobiler7c]

Thanks hopefully its the alternator i will check it tomorrow when the weather breaks any tips on a possible upgrade from stock? thanks
Mark

[snowmobiler7c]

Ok got batteries back in truck today and started it im pushing 13.38 to 13.40 IS that close enough to 13.5 or should i have the alternator bench tested?? thanks
Mark

[NoRalPh]

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.

[snowmobiler7c]

It was origionally at night, we had been driving with lights, radio, and heater all on. After I posted this, I went back outside. Turned on headlights, heater, radio and 4 ways. Voltage dropped to 11.4, went to autozone tested alternator and they said failed. I just got a new one and hope to put it on tonight after dinner. Thanks
mark