Alternator swap

Tiny
DUANE JOHNSON
  • MEMBER
  • 1997 FORD F-150
  • 4.2L
  • 6 CYL
  • 2WD
  • MANUAL
  • 205,000 MILES
Can you put a 1997 g150 4.2 alternator on a 2001 f150 5.4?
Wednesday, July 3rd, 2019 AT 10:42 AM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,752 POSTS
No. If you look up the part numbers for both applications, you'll see they are completely different. A visual comparison shows the mounting systems are not even close to the same.

When you find a replacement generator that will bolt onto the engine, you first have to look at the number of grooves in the pulleys to see if that matches your belt, then an often-overlooked difference is the maximum output current. An AC generator is physically incapable of developing more output current that it is designed for. If the replacement has a lower maximum output current, no problems will occur. When people install a replacement with a higher output, in the misguided thinking it is going to do something better than the old one, it too will work normally until someone performs a charging system test to include that maximum full-load output current test. At that point the current can exceed the rating of the very large fuse bolted into the under-hood fuse box. Once that fuse is blown, there will be no output current from the generator.
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Wednesday, July 3rd, 2019 AT 11:03 AM

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