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Bumpin' Yota · 03-21-2006, 10:38 AM

Quote:

Originally Posted by snap-on

I have a few issues with the above.

1) generally im trying to get my alternator tested because i think its not working ie its output is nearly 0 amps. so even a puny 20 amps at idle is more than 0 and at least SOME indication that the alternator is working.

2) he talks about instantiously applying a (test) load to the alternator and some how this is unreaslitic? ummmmm oddly enough its JUST like when i flip the switch on my 4 140w daylighters! there is no, they dont come on kinda dim then finally get bright, BOOOM they are on and drawing 40 amps. THe regulator CIRUCUT (ie electrionics) is just that, electronics, capable of "responding" in fractions of a second. So why there may be a fraction of a sec that the lights draw off the battery, the alternator SHOULD be able to ramp up output with in a sec or less.

I have always considered autozone/advance whatever that test alternators as is it DOA? not "is it still capable of putting out full design rated current"

Well how I am able to tell is with a DMM measuring the voltage at the battery. If the voltage with the engine off is around 12.9v, then you fire up the engine and the voltage increases to say, 13.5v, then yes your alt is working.

I think what dom was referring to as far as load testing the alt is not a meager 40 or 80 amp draw, but rather a draw that is much higher than what the 160+ amp alt can provide. If one monitors the system voltage during testing and has a good clamp meter to measure current flow you can determine at what point the alt cant put out any more current. He was saying that such a severe load should be applied gradually not all at once. The same concept would hold true for a manual tranny truck...do you bounce off the revlimiter and dump the clutch all at once while towing a 20,000lb trailer with your tacoma to see how far you can move it? (God I hope not...lol)