Alternator swap

1994 FORD RANGER
109,000 MILES • 2.3L • 4 CYL • 2WD • MANUAL
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GOGOJUICE6
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  • 76 POSTS
I just replaced my alternator for a 200A one (according to manufacturer). I'm trying to check amps with a clamp meter but the readings I'm getting are too low. I know I must be doing something wrong (hopefully) Can you refresh my memory on how to check amps output from alternator?
Thanks for your help.
Al
Feb 17, 2022 at 11:26 PM
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SQM
  • ✓Experienced Mechanic
  • 6,383 POSTS
Hello,

Were you checking the amperage at idle? At idle the amp will be much lower than the rated max output of 200 amp.

In order to test the amp rating with a clamp you will need to use a carbon pile load tester along with the clamp. Put the clamp on the positive output wire of the alternator, star the engine and have the idle at 1,500 RPMs. The carbon pile will simulate an engine load and the alternator output should increase to the rated amperage.

I attached a picture of a typical load tester.
Please let me know if you have any questions.
Thank you.

https://www.2carpros.com/articles/how-to-check-a-car-alternator
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Feb 18, 2022 at 12:36 AM
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GOGOJUICE6
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Sean, as always, very helpful tips. Unfortunately, I don't have one of those. but thanks a lot for the help. I keep saying you guys are second to none.
Feb 18, 2022 at 9:10 AM
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SQM
  • ✓Experienced Mechanic
  • 6,383 POSTS
You are welcome and your support is much appreciated!!
Feb 18, 2022 at 12:14 PM
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