Why Your Local Autoparts Store Cant Test Your Alt Properly

[8000watts]

i love the vid of steve messing with the autozone kid classic any way awesome post

lol "Its not givin me an accurate readin cuz u kno, u got all these god damn alternators on it!" lol

[F540HD]

Dom,

Are you serious? You really think no rebuilders are smart enough to test a high output alternator? I use a snap-on for testing on vehicles that displays over 400 charging amps and doesn't use aligator clamps. Please climb off your high-horse and enjoy a little reality. I see alternators pass over my bench that will make over 300 amps each. I'd love to test one of your units and be honest about what the performance level truly is.

Bill

[jbondox]

Well I am glad someone hoisted the BS flag

My favorite is when being tested, when calling the company that "manufactured" it, makes excuses, not enough rpm's... voltage regulator needs adjusting.... the pulley is the wrong size... Sounding familiar yet?

[michigancapri92]

off topic but dlesman i like your avatar !!! reminds me of my father ...... *facepalm

[tprice07]

I had napa test my alt..they said it failed...i had advanced test it and the guy testing it shot back and said woaahh your overcharging buddy...I laughed and said nope that's an HO alternator. My alt was rated 250 amps and on their test was doing 220 amps..I'd imagine it was fairly accurate all things considered.

[MECHMAN]

Many of the new testers will fail a unit if the voltage is outside OEM spec, meaning that if your aftermarket regulator charges at 15.2v cold and settles to 14.8v hot that it may show a regualtor failure if the spec allows for a max of 14.6v.

Most of the aftermarket test equipment can only pull about 200a from their load bank or their meter won't read high enough to show true output. While you may not see the full output on a test bench that does not have the full load capability. Remember that the amperage output will not reduce unless there is a failed part such as a diode or worn brushes.

I'm keeping this very general, this is more complicated than I am explaining it here, but the general information is really what will serve you best in testing your unit.

There are exceptions to this, but if you have your system connected in your vehicle you only need a couple tools to test your alternator charging output yourself. The DC amp clamp isn't cheap, so you might want to borrow one, but any audio enthusiast should have a quality voltmeter.

Using your system in place of a load bank may not max out your alternator output, but you will be able to see the output that it is producing, and using the voltmeter you can monitor voltage to determine if there is in fact an alternator problem.

We have a 400a load bank in our shop that we use on our test bench and a 400a amp clamp to read accurate amperage output. If anyone needs a unit tested we can do this for you. You pay the shipping and I will test the output of your high output alternator if you can't get it done locally.

[snafu]

Good stuff Matt. Mechman = value add. And, that's why they're our partner.

[fatdaddy1999]

Thanks good info.

[bassman619]

Just a side note..DO NOT try to test amperage with the dc or ac amps setting on a digital multimeter..most dmms can only read currentin the miliamps range..meaning less than 1 ampere..if u try to read alternator amperage with a dmm you will fry ur dmm and possibly catch it on fire..just wanted to mention in case anybody gets that bright idea..haha

[DrunkenwhippeT]

One thought I have in regards to local shops bench testing alternators...

In order for an alternator to give a certain power output, it needs an equal power input. One horsepower is equal to 745.699872 watts. 745 watts at 14V is 53.2 ish amps. 200 amps at 14V is 2800 watts, or about 3.75 horsepower. This isn't taking into account losses in bearings and belt friction. I'm doubtful that the average bench test setup has an electric motor that can sustain nearly this much power output without tripping it's overload protection.

I'm pretty new to the competition audio world, doesn't anyone run current shunts in their alternator outputs for monitoring? I see people run voltage meters, but never current. I'm not planning on competing, but I do plan to run one on my alt, and probably one on the battery too once I start a real build.