2007.5-2009 Dodge 6.7L Cummins Charging & Starting Parts

Charging and starting on the 2007.5-2009 Ram 6.7L Cummins

The 6.7L Cummins in these trucks runs two 12-volt batteries wired in parallel, one on each side of the engine bay. A single belt-driven alternator keeps them charged, and it rides on the serpentine belt, which the maintenance schedule calls for at 100,000 miles. A gear-reduction starter turns the engine over against 17.2:1 compression. There are no glow plugs. Cold starts lean on an electric grid heater in the intake, and that heater keeps cycling after the engine fires on a cold morning.

That grid heater is the key to understanding this system. It is a heavy electrical load, heavy enough that aftermarket intake heaters for this engine are rated in the 750-watt range. When a battery is tired or a cable end is corroded, the grid heater is what exposes it, and the complaint usually sounds like a starting problem. Body electrical, from lighting to relays, runs through the TIPM (Totally Integrated Power Module) under the hood.

What fails and why

The TIPM is the documented electrical weak point on 2008 trucks. Owners of 2008 Ram 2500s report it losing power at random to electrical components. The symptoms they describe are accessories or lights dropping out, the fuel pump cutting out, relays clicking and a no-start. These are owner reports rather than a factory bulletin, but the pattern is consistent enough that the TIPM belongs on the list for any electrical problem that comes and goes.

Battery cables are the next suspect. Owner complaints on 2008 trucks include battery cable and instrument cluster problems that show up as intermittent gauges, hard starting and low voltage. The grid heater circuit adds its own wear: a corroded heater stud or cable brings slow cranking in the cold, voltage dips and grid heater codes, and a loose heater stud is a mechanical risk on top of the electrical one. On a truck this age, corrosion on the heater and cable connections is the first thing to look for.

Stock replacement vs. upgrade

Start with the simple checks. Slow cranking is usually the batteries or the cables before it is the starter, so test both batteries and inspect every cable end before you buy a starter. When the batteries go, replace them as a matched pair. Putting one new battery next to an old one on a dual-battery diesel shortens the life of the new one. While you are there, clean or replace the grid heater connections and the battery cables.

The alternators and starters here are sold as heavy-duty or high-output replacements. If you have added lighting, a winch or other accessories, a high-output alternator gives the charging system more room. We do not print a factory alternator rating for these trucks, so compare against the tag on your old unit or check by VIN rather than trusting a number from a forum.

What we carry

XDP supplies most of this collection: the XD354 HD high-output alternator and the XD259 HD gear-reduction starter, both in a wrinkle black finish, along with the XD421 HD alternator cable, the XD422 HD high-output alternator cable, the XD445 HD replacement battery cable set made for 2007.5-2009 trucks, and the XD534 starter bolt kit in black phosphate. Mean Green adds the 9029 gear-reduction starter and its 1391 and MG1391SHD high-output alternators, the latter rated at 375 amps. Lucas Oil Sure Start starting fluid (11238) is here for owners who keep a can in the truck; read the directions on the can and your owner's manual before using any spray starting aid on a grid-heater engine.

Fitment notes

This collection is for the 2007.5-2009 Ram 2500 and 3500 pickup with the 6.7L. A 2007.5 truck is a 6.7L; earlier 2007 trucks have the 5.9L common-rail, which is a different engine. Several parts here are listed for wider ranges: the alternator cables list 1994-2018 5.9L and 6.7L Cummins, the starters and alternators list ranges that run into later 6.7L years, and the XD445 battery cable set is specific to 2007.5-2009. The 4500/5500 chassis cabs are a different chassis and most pickup parts do not interchange, so read the product fitment before ordering for a cab-and-chassis truck. For alternators and starters, verify by VIN.

Frequently asked questions

Why does my 6.7L Cummins crank slowly on cold mornings?

Start with the batteries and cables, not the starter. On these trucks slow cranking is usually a battery or cable problem first. The intake grid heater is a heavy load in the cold, and a corroded heater stud or cable shows up as slow cranking, voltage dips and grid heater codes. Test both batteries and check every connection before you replace the starter.

Do I have to replace both batteries at the same time?

Yes, replace them as a matched pair. The two batteries work in parallel, and a mismatched pair shortens the life of the newer battery. It is also a good time to clean or replace the battery cables and the grid heater connections.

My 2008 Ram has random electrical dropouts. Is it the alternator?

Maybe not. Owners of 2008 trucks most often trace random loss of power to accessories, lighting dropouts, relays clicking and no-starts to the TIPM, the power module under the hood. Battery cables and connections are the other common cause. Check those before you condemn a charging system that may be doing its job.

Does the 6.7L Cummins use glow plugs?

No. The 6.7L uses an electric grid heater in the intake as its cold-start aid. That is why battery and cable condition matter so much on this engine: the heater draws hard on the batteries for the start and keeps cycling after the engine fires.

What does the serpentine belt have to do with the alternator?

The alternator is driven by the serpentine belt, and the maintenance schedule for the 6.7L calls for that belt at 100,000 miles. If you are replacing an alternator on a high-mileage truck, look the belt over while it is off.

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.