2004.5-2007 Dodge 5.9L Cummins Alternators

Alternators for the 2004.5-2007 RAM 5.9L Cummins

The factory layout is simple: one alternator, two 12-volt batteries and a gear-reduction starter. What makes the alternator work is everything hung on it. The common-rail 5.9L Cummins in these third-generation trucks is fairly electronic, with a lot of sensors and relays, and the grid heater pulls heavy current through its relays before the engine fires. Once the truck is running, the alternator has to put all of that back.

When to replace or upgrade

A charging problem often surfaces first as a weak battery, and on this engine a weak battery shows up as a long crank. The ECM will not fire the injectors until rail pressure reaches roughly 4,300-5,800 psi, and slow cranking stretches that out. So before you buy an alternator, test both batteries and the charging output, and know which part is actually tired. If the batteries are good and the truck still cranks long, the cause is more often on the fuel side, rail pressure and injector return, than the starter.

The upgrade case is added load. High-output alternators are offered for these trucks for owners running extra accessories or an aftermarket lift-pump system. We could not confirm the factory amp rating for this platform, so check your build sheet or VIN if you want to compare numbers before you choose.

What we carry

• Mean Green 1398 high-output alternator, listed for 2003-2007 5.9L Cummins trucks.
• Mean Green MG1398SHD, rated at 375 amps, for the same trucks.
• XDP XD512 heavy-duty high-output alternator in wrinkle black, also listed for 2003-2007.

If you are stepping up in output, plan on the charge cable too. XDP's heavy-duty high-output alternator cable sits in the Charging/Starting parts collection for this truck.

Fitment notes

The alternators here are listed for 2003-2007 5.9L Cummins trucks, which covers the whole 2004.5-2007 run. Model year 2007 is shared with the 6.7L, which went into trucks built after January 1, 2007, so confirm you have the 5.9L before ordering. Verify by VIN, and if you have added accessories, add up what they draw so you can pick an alternator with room to spare.

Frequently asked questions

Will a high-output alternator fix my long crank?

Only if undercharged batteries are the cause. Test both batteries and the charging output first. If the batteries are healthy and the crank is still long, look at rail pressure and injector return, which are more often behind long cranking on this engine than the starter.

What was the factory alternator rating on these trucks?

We could not verify it for the 2004.5-2007 5.9L, so we do not quote one. Your build sheet or a VIN lookup will tell you. The high-output units here are listed by their own ratings, such as the 375-amp Mean Green MG1398SHD.

Why upgrade if my stock alternator still works?

You do not have to. The case for a high-output unit is added load, like an aftermarket lift-pump system or extra accessories, on a truck that already runs a grid heater and a lot of electronics. If your truck is stock and charging normally, replace the alternator when it wears out and move on.

Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.