I am getting ready to go on about a 1200 mile road trip, up to Atlanta, over to South Carolina and back home again. I was checking over my truck today, looking for any potential problems before I hit the road. I checked my battery/alternator with the truck idling and no electrical accessories turned on I had 13.65 volts across the battery terminals. I turned on the AC full blast, high beams and driving lights, at idle I had 13.45 volts, rev the throttle by hand up to about 1500 RPM and I had 13.65 volts again. This tells me that my alternator is working OK. I think I would have a higher voltage reading from it though if it were a colder temperature outside. It was about 95 degrees today.

This is on my 3.9 with a 5-speed manual. 145,500 miles on it, I am still running my original Denso 117 amp alternator, and I put a Duralast Gold battery in my truck last summer. I am just wondering if anyone else has any different output from their alternator.

Thanks for any info here.

Jimmy

 

That's just fine for low speed. Ideally you want about 14.4, but that may not be until 20-2500 RPM. The computer will also back it off a little in the heat. I think you're fine.

 

Thanks. I think it is OK too, I was just wondering if anyone else had anything different from their alternator or electrical system. Today I checked mine and the rest of my truck too just to be sure everything was in good shape and working OK. I put in a new air filter, new pcv valve, new wiper blades, topped off my washer fluid, checked all my tire air pressures, including the spare, I changed my oil and manual transmission lube too. My truck is running great and shifting very smooth right now.

I don't run a lot of electrical accessories, just a JL Audio 300/4 amplifier, and I don't play my system loud very much at all, and even then it's only for one or two songs, then I turn it back down to a normal volume. I don't use my driving lights much either, but they are good to have when I need them.

Jimmy