Alternator question

[supldys]

Quick question if anyone can answer it, trying to determine if my alternator is at fault here.

My battery goes bad every year, almost clockwork. Got my alternator tested and its putting out 13.8v and 4.9amps no load, 14.3v and 4.9 amps under load. The volts look good, but those have got to be some low amps, its just weird that under load its not changing at all. Any idea what could be causing that? But it appears to not be putting out enough juice to fully charge the battery.

Thanks.

[Geeesammy]

My hillbilly way helps diagnose a little bit.

 

Turn it on, and literally turn on anything electrical you can. Wipers on full tilt, rear defrost, hazards, brights, a/c, blower on high, fog lights, etc. Then check your amps and volts, they shouldn't falter much if it is a good alternator.

 

In my opinion if you are going through batteries that fast you've got something going on unless you do a LOAD of starting/driving. Take the alternator off and have it bench tested at a parts store and go from there, but if it was me I would replace the alternator anyways if you have some doubts about its capabilities. I'm sure a professional will disagree but I'd replace both and hopefully the battery is still under warranty.

Edited October 24, 2013 by Geeesammy

[Not Brian]

I'd just replace it anyways since it's like $150.. a new battery costs about that much.

[AndMetal]

Pretty sure you should be putting out about 20x the current (90+ amps depending on the vehicle). I vote for a new alternator.

[Cordell]

And how are you testing it for Amps? 4.9 loaded and unloaded just makes me question how you are coming to that. If there is only a 4.9 amp load that's all you're going to read. Batteries are much easier to have issues with, and depending on the car's use can be very hard on a battery. Not saying its a battery but I would double check the alternator, maybe have it bench tested.

[supldys]

I'll probably pull it off and take it in just to check. The test was one of the mobile testers at Advance Auto, definitely not as accurate as a bench tester.

Luckily the battery is under warranty for another year, so I want to figure this out before I have to dish big bucks for another one.

Thanks guys

[Mensan]

Your alternator does not determine current. Whatever is plugged into it does. If you exceed the capacity of the alternator, voltage will drop, and current will as well.