On the aluminum-body F-150 the alternator is mounted high on the passenger side and is one of the friendlier charging-system jobs in a modern truck. The 5.0 V8 and the 3.3/3.5 naturally aspirated V6 give you enough room to work almost entirely from above with a 3/8 in ratchet, a few extensions and a belt tool. The 2.7 and 3.5 EcoBoost are tighter: the intercooler plumbing, coolant degas bottle and air deflectors crowd the area, so plan on 20-30 extra minutes of parts removal on each end of the job.
The two things people get wrong are the belt and the B+ stud. Take a photo of the serpentine routing before you release the tensioner, because these engines have several idlers and a belt one groove off will shred fast. And torque the B+ output nut with an inch-pound wrench rather than reefing on it with a ratchet, since over-torquing that stud cracks the regulator housing and causes intermittent no-charge faults. Also confirm whether your 3.5 EcoBoost truck was built with the dual-alternator option before you order a part.
| Item | Type | |
|---|---|---|
| Socket set, 3/8 in drive 8, 10, 13, 15, 18 mm 6-point sockets Battery terminals, B+ output nut, alternator mounting bolts and tensioner/idler bolts. | Required | shop |
| Ratchet, 3/8 in drive Standard and stubby Main driver for all fasteners; stubby helps in the tight EcoBoost bay. | Required | shop |
| Extension set 3, 6 and 10 in, 3/8 in drive Reaches the lower alternator bolt and B+ terminal behind the accessory bracket. | Required | shop |
| Swivel / wobble extension 3/8 in drive universal joint Angles the ratchet onto the rear alternator bolt without removing more parts. | Recommended | shop |
| Serpentine belt tool Long-handle belt tool kit with 3/8 in drive and 15/18 mm crowfoot sockets Rotates the spring-loaded belt tensioner to release the serpentine belt. | Required | shop |
| Breaker bar 3/8 in drive, 18 in Alternative to a belt tool for swinging the tensioner if you have clearance. | Recommended | shop |
| Torque wrench 3/8 in drive, 5-80 ft-lb Alternator bolts thread into aluminum brackets and must not be overtightened. | Required | shop |
| In-lb torque wrench 1/4 in drive, 20-200 in-lb For the B+ output stud nut, which is a low-torque spec. | Recommended | shop |
| Trim / panel pry tool set Plastic Pops the intake duct clips, engine cover and wiring harness retainers without breaking them. | Recommended | shop |
| Flat screwdriver set Small and medium flat blade Releases the plastic locking tab on the alternator regulator connector and loosens duct clamps. | Required | shop |
| Nut driver or 7 mm socket 7 mm / 5/16 in for worm-drive hose clamps Loosens intake duct and degas bottle hose clamps on EcoBoost trucks. | Recommended | shop |
| Flashlight / headlamp LED The lower mounting bolt and belt routing are hard to see from above. | Recommended | shop |
| Phone camera Photograph the belt routing before removal; the 2.7/3.5 EcoBoost routing is easy to get wrong. | Recommended | shop |
| Multimeter DC volts Confirm the old unit is bad and verify 13.5-14.8 V charging after the swap. | Recommended | shop |
| Serpentine belt Engine-specific; replace if cracked or over 100k miles The belt is already off, and a glazed belt will squeal on the new pulley. | Parts | shop |
| Alternator Engine-specific; 150/200 A, note dual-alternator option on 3.5 EcoBoost The replacement unit; match amperage and connector to your build. | Parts | shop |
| Battery terminal brush or cleaner Clean the negative post and cable before reconnecting. | Consumables | shop |
| Dielectric grease Small tube Protects the B+ stud and regulator connector from corrosion. | Consumables | shop |
| Safety glasses Debris falls from the belt area when reaching over the engine. | Safety | shop |
| Nitrile gloves Keeps hands off hot exhaust residue and dirty belt dust. | Safety | shop |
2.7 and 3.5 EcoBoost need the intake duct, coolant degas bottle bracket and often an intercooler air deflector removed first, which adds 7 mm hose-clamp and 8/10 mm bracket fasteners; the 5.0 V8 and 3.3/3.5 NA V6 usually only need the intake duct and engine cover. Mounting bolts are 13 mm on most builds but some brackets use 15 mm, and the belt tensioner takes either a 15/18 mm hex or a 3/8 in square drive depending on the tensioner supplier. 3.5 EcoBoost trucks with the heavy-duty/upfitter package can have two alternators with different mounting hardware and cabling.
| Alternator mounting bolts (M8, most engines) | 18 ft-lb (25 Nm) - verify in the service manual |
| B+ output terminal nut | 89 in-lb (10 Nm) - verify in the service manual |
| Battery negative terminal clamp | 71 in-lb (8 Nm) - verify in the service manual |
| Belt tensioner mounting bolt | verify in the service manual |
| Engine appearance cover / intake duct bolts | verify in the service manual |
Mounting hardware on this generation is almost always 13 mm with a 10 mm B+ nut and 8 mm battery terminals, but a few brackets use 15 mm and tensioner tools vary between 15 mm, 18 mm and 3/8 in square drive, so test-fit before committing and confirm torque values against the Ford workshop manual for your exact engine.
With the engine running at idle, battery voltage should be about 13.5-14.8 V; a reading near 12.4 V or below with the engine running points at the alternator or its wiring. A no-charge code, a battery light, or dimming lights that change with engine rpm all point the same way, but load-test the battery too since a failing battery can trip charging faults.
No registration is required like on some European cars, but the 2015-2020 F-150 uses a battery monitoring sensor on the negative cable that relearns state of charge over time. Let the truck idle for several minutes and drive it normally; if you also replaced the battery, a BMS reset with a capable scan tool such as FORScan is worth doing.
Yes. Rotate the spring-loaded tensioner with a serpentine belt tool or breaker bar to slip the belt off the alternator pulley. Photograph the routing first and inspect the belt while it is off, since it is only a few dollars more to replace it while you are there.
Ford offered a dual-alternator setup on 3.5 EcoBoost trucks ordered with the heavy-duty electrical or upfitter/police packages to support added loads. Verify which unit is faulty before ordering, and check the amperage and connector type against your build sticker or VIN.