What to look for when buying an alternator

[loopkiller 10+ year member]

I don't have much to say about brands, but idle output is what you should focus on. Ask them to back up their claims with some testing to be sure it will perform at spec. Most of the major guys you have heard of can do that. If they have no testing equipment, look for someone who actually has it.

 

[HCCA 10+ year member]

Listen to DBBOOM. He's got it right. And, yes, idle current is what's important.