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How do I check the alternator’s rating?

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=31728
Printed Date: April 29, 2024 at 7:17 AM


Topic: How do I check the alternator’s rating?

Posted By: toyota_4runner
Subject: How do I check the alternator’s rating?
Date Posted: May 06, 2004 at 6:03 PM

In my 1986 4runner, the stock alternator would have 60 amp rating. However, I can see that the previous owner had installed amp(s) in this truck, since there is an amp wire coming into the cabin (he also saved my time!!) I am thinking there is a possibility that he changed the alternator. Is there a way to check , eg by connecting any particular terminals with a multimeter, what is the ampere rating of the alternator?

Also, I need to find if I really need a higher amperage alternator/capacitor.

I did some calculations based on info given in the website below but since I am new I would appreciate if someone can check /correct it

https://www.crutchfieldadvisor.com/S-t3IOSMYH2Ll/learningcenter/car/amplifiers_faq.html

My amps: Kenwood KAC 8401: 60W X 4 RMS = 240 RMS (for speakers)

                   MTX 275 X : 150W X 1 RMS (for the 8 ohm subs bridged at 4ohm )

So total power= 390 W, multiplying by 2 for amp's inefficiency, power = 780W

Dividing by 13.8 V (average voltage) , current = 56.52 A

divinding by 3 to get average current, 18.8 A

Seems like I dont need any high current alternator or capacitor. AM I right? If not what do you suggest if my alternator is a 60 amp alternator?




Replies:

Posted By: toyota_4runner
Date Posted: May 07, 2004 at 9:17 AM
writing just so that it comes on the front page and someone sees it to reply. Thanks!


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