5.9 and 6.7 Cummins Serpentine Belt Diagrams With and Without AC
A 6.7 Cummins serpentine belt diagram is not interchangeable with a 5.9 Cummins serpentine belt diagram. Ram trucks with the 5.9 24-valve and 6.7 Cummins diesels use different accessory drive layouts by model year and whether an air-conditioning compressor is installed. The Cummins 6.7 serpentine belt or 24-valve 5.9 routing must match the truck, including every idler and the automatic belt tensioner.
Identify the Truck and Accessory Configuration Before Choosing a Diagram
Model year, engine identification, and the accessories actually bolted to the front of the engine decide which 6.7 Cummins serpentine belt diagram or serpentine belt diagram 5.9 Cummins applies. A 5.9 and a 6.7 Cummins accessory drive belt can share a similar look from a distance, yet pulley count, tensioner location, and compressor presence change the path. Confirm the engine family from the underhood labels and build data, then match that information to vehicle-specific service information rather than a generic Cummins sketch.
Look for the belt routing decal in the engine bay and compare every depicted pulley to what is installed. The drawing should show the same crankshaft pulley, automatic belt tensioner, idler pulley positions, and AC compressor pulley if a compressor is present. Switching the air conditioner off does not change routing on an AC-equipped truck; a truck without a compressor is a different configuration. Displacement alone cannot set the belt path or replacement fitment, because two 6.7 or two 5.9 engines can carry different accessory packages.
Locate the Correct 5.9 24-Valve Cummins Belt Routing
The 24 valve 5.9 Cummins serpentine belt diagram applies only to the 24-valve 5.9 diesel used in Ram trucks of the years that received that engine, not to every Cummins 5.9 ever built. Confirm the truck's model year and accessory arrangement before treating any Cummins 5.9 serpentine belt diagram as a match. Earlier 12-valve layouts and later 6.7 drives are separate families. Read the applicable drawing by finding the crankshaft pulley first, then the automatic belt tensioner, any idler pulley, and each driven accessory shown.
The diagram traces the belt path around those pulleys and shows which face of the belt contacts each one. The ribbed belt surface typically rides in grooved pulleys, while a smooth pulley contacts the back of the belt. Do not assume one route for every 5.9 application, because AC and non-AC trucks, extra idlers, and year-to-year accessory changes alter the wrap. If the belt routing decal is missing, unreadable, or shows pulleys the truck does not have, obtain matching service information for that VIN and configuration before installing or rerouting a belt.
Confirm the 6.7 Cummins Belt Diagram With AC
A 6.7 Cummins serpentine belt diagram with AC must be matched to the specific Ram application and the accessory drive that is actually installed. Identify the AC compressor pulley on that drawing, usually a grooved pulley for the compressor clutch, then trace the complete path of the serpentine belt 6.7 Cummins from the crankshaft around the tensioner, idlers, and remaining accessories. Confirm that the same compressor is present on the truck. An AC-off switch setting is irrelevant here; the belt still wraps the compressor pulley whenever that unit is part of the drive.
With the engine off and cool, compare the diagram's automatic belt tensioner and idler locations with the hardware you can see. Belt alignment depends on those pulleys sitting in the positions the drawing assumes. If the 6.7 Cummins serpentine belt is damaged or missing, do not reconstruct the route from pulley positions alone. Empty pulleys can be misread, extra idlers can be leftovers from another layout, and a guessed wrap can leave the belt off a water pump or alternator. Use verified routing information for that truck before a new belt is fitted.
Verify Non-AC Routing and Existing AC Bypass Modifications
A non-AC 6.7 Cummins serpentine belt diagram or a 5.9 Cummins serpentine belt diagram without a compressor is valid only when that route is documented for the exact application. Do not assume a factory non-AC configuration exists for every Ram diesel. Where the factory accessory drive included a compressor, a shorter belt and a different wrap may not be a documented option. Removing or bypassing a compressor does not by itself establish a correct belt route or a correct belt length for the remaining pulleys.
A modified accessory drive needs documentation that lists the installed components, including any substitute idler used in place of an AC compressor pulley. If that documentation is unavailable, a qualified technician should assess the drive before a belt is ordered. Pulley clearance, ribbed-to-groove contact, wrap on a smooth pulley, and the automatic belt tensioner's operating range cannot be validated by appearance alone. A belt that looks tight can still sit outside the tensioner's designed arc, which leads to slip, edge wear, or loss of drive to critical accessories.
Confirm the Replacement Belt and Plan Safe Service
Confirm replacement fitment through vehicle-specific parts information that accounts for engine, model year, installed accessories, and any documented modification. A Cummins 6.7 serpentine belt and a 5.9 accessory drive belt are selected by that application data, not by displacement nicknames. Markings on the installed belt can support identification, but they are not proof of correct length or rib count, because a previous owner may have fitted the wrong part. Match the new belt to the verified routing diagram so ribbed surfaces land on grooved pulleys and the back of the belt meets any smooth pulley.
Prepare for service by parking the truck on level ground, securing it against roll, and allowing the engine to cool. Follow the vehicle's service information to prevent accidental starting, and keep the verified routing reference at the work area so the path is not reconstructed from memory. The automatic belt tensioner stores spring force, and access around the 5.9 or 6.7 accessory drive can be tight. Those conditions create pinch and impact risks. When the required procedure, tools, or lockout steps are uncertain, leave tensioner manipulation and belt removal to a qualified technician.
Inspect Belt Seating and Recognize Problems That Need Testing
Parked and cooled, the accessory drive belt can be checked for frayed edges, missing ribs, glazing, oil or coolant contamination, and a belt sitting outside pulley grooves. Those observations indicate a seating or alignment problem that the 6.7 Cummins serpentine belt diagram or 5.9 routing drawing can help interpret, because they show where the ribbed belt surface and the back of the belt should rest. Squealing, chirping, or repeated belt damage can come from misalignment, a sticking pulley, contamination, or tensioner issues. Sound alone cannot identify a failed tensioner or accessory.
After any belt work, perform an engine-off seating check against the applicable diagram. Confirm every wrap, the tensioner pulley contact, and that the belt is fully in each groove. Keep hands and tools away from a running accessory drive. Stop driving and arrange assistance if the belt is lost, the engine overheats, or steering assistance changes suddenly, because those symptoms can follow a dropped serpentine belt on a 6.7 or 5.9 Cummins. Professional testing should resolve underlying pulley, bearing, or accessory faults rather than treating a damaged belt as the complete diagnosis.