Bad Altenator?

[stantjeeper85]

Altenator does not appear to be charging my batteries. The batteries are not the problem as they are brand new, the cables and wires appear to be in good shape. If those two things are OK then the only thing left is the alternator, right? could it be anything else?

Perhaps the altenator is not strong enough for the engine. It is the same alt that was on the 1/2 ton light duty 6.2 before the prev owner installed the heavy duty military 6.2 (im guess humvees are 1 tons). I checked new alts at autozone and the light duty versions run at 83 amps while the heavy duty alts run at 105 amps. could the weak alt finally have given up?

Also, i need the truck to get to work tomorrow (tuesday) - friday. 4 days. but i cant replace the alt until this weekend. commute is only 30 miles one way. I only need to start the truck 4 times throughout the day. Since the engine/truck is mechanically driven and does not need batteries or alt to move once started, im thinking about keeping the batteries on a charger throughout the night each night so that each morning starts out with a full charge. the batteries are both yellow top optima deep cells, so they should be able to handle 4 starts each day on a full charge. I should be able to limp my way through the week this way. Will it work?

thanks for the input guys.

ps - ill be getting the serial # for the engine up here tonight.

[john8662]

You have two options for diagnosing the alternator.

Get ahold of a Digital Mulimeter and read voltage with the engine running, you should see upwards of 13.8 - 14 volts, if not, alternator isn't working.

The other way is to take the tools necessary with you to your local auto parts store that tests them, remove outside, take inside, test. If fail, replace.

There isn't a problem with the 80amp alternator, on just about every 6.2, and works fine with two batteries all day long.

Check your connections, you may even want to measure voltage with the truck not runing at the output terminal of the alternator, to ensure that the wire is indeed connected to the rest of the electrical system.

You can probably get around 4 starts with one charge, for sure if you have the gear reduction starter, less with the direct drive.

J

[stantjeeper85]

You have two options for diagnosing the alternator.

Get ahold of a Digital Mulimeter and read voltage with the engine running, you should see upwards of 13.8 - 14 volts, if not, alternator isn't working.

The other way is to take the tools necessary with you to your local auto parts store that tests them, remove outside, take inside, test. If fail, replace.

There isn't a problem with the 80amp alternator, on just about every 6.2, and works fine with two batteries all day long.

Check your connections, you may even want to measure voltage with the truck not runing at the output terminal of the alternator, to ensure that the wire is indeed connected to the rest of the electrical system.

You can probably get around 4 starts with one charge, for sure if you have the gear reduction starter, less with the direct drive.

J

If it is indeed the alt that died, would it be worth it to upgrade to the 105 amp? $85 from autozone not bad. As they say, whenever something breaks, always upgrade!