My car's amp pull?

[Insomniac119 10+ year member]

Is there a way to find out how many amps my car is pulling from my alt whith all the electronic accessories on? I have an 81 Buick Riviera, 252 V6 (Chevy) weak *** motor, and my alt is 70 amps. When I turn my heater on at night my lights dim for half a second or so, if that's any kind of indication. But there is nothing else like that i've noticed.

I went to Advance Auto Parts and all he told me was that I needed an new battory (which i didn't). Maybe next time I'll try Auto Zone, I like them alot better.

I guess what i'm asking is if there's a rule of thumb, or chart or anything I can look at.

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[jrz126 10+ year member]

autozone has a free batt/alt tester that they hook up to your car, the car has to be running for the test, so just be sure to have your accesories turned on. They should be able to tell you how many amps you're drawing.

I dont think you have to worry about anything, my dash lights dim a bit when I have my rear defroster running.

 

[n2audio 5,000+ posts]

There's a general rule of thumb in the automotive industry that there should be about 40% overhead when the car is at full electrical demand. So with your 70A alt - 70x.4 = 28A

So you can figure engine/heater/lights/accessories all on it will require roughly 40A.

 

[Insomniac119 10+ year member]

thanks