Let me start by saying this response is to the supplier, not you.
That doesn't just step on toes, that's a direct insult.
Your hometown rebuilder.
1. They are just that, a rebuilder. They know very little about the design and function of an alternator. They just repair factory alternators by replacing parts. They also will tell you your crazy when you tell them an alternator can do 200 amps. They dont understand what they dont know.
I'm a hometown rebuilder. I deal with tech people at regulator and diode manufacturing facilities to explain problems that arise from modifying computer controlled charging systems and have a thorough understanding of what makes them work and how to improve them.
2. When they do test an alternator,(on their bench), they almost always use small aligator clips to the battery post of the alternator. Probably 8 or 6 gage. Would you connect your 2000 watt amplifier to your battery with 8 gage? I dont think so....for obvious reasons.
I'd rather test the alternator on the vehicle where i can see it perform in a real world situation however my bench is setup to replicate it quite close. I use bolt on terminals for anything over 100 amps.
3.On their bench test, they more than likely will never go over 3500 to 4000 rpm. Dont freak out, this is alternator rpm, not engine rpm. An alternator should spin atleast 3 times faster than your motor. The industry standard for max output is to be tested at 6000 rpm. Approximately 1500-2000 engine rpm. 3500-4000 is just above idle.
My bench has a 5hp 3 phase motor with a 6" pulley to a 2" pulley. I can spin an ambulance alternator at 15,000rpm but most troubles are at idle.
4.When a load is applied, it should be gradual. 75% of the test stations that are common to rebuild shops are either on.... or off when it comes to loading. (typically 300 amps) There is no way to ramp up the load presented to the alternator. When you load an alternator with an instantaneous 300 amps, the regulator does not have time to react and the reading will be substantially lower. It also depends on the type of regulator used. Some vehicles must have a time delay type regulator due to the car either being so new or aftermarket not available yet. When you load the alternator down, you keep going until the voltage level falls to that of the battery. Which is typically 13.0-13.5 This way all current being pulled is is being produced by the alternator, not the battery. You then take the current reading off the battery post of the alternator.
You may notice this tester has a knob and no switches. It is applicable up to 600 amps. You can adjust how quick the load comes on by how fast you turn the knob. For accurate high amps readings it must be tuned like an old am radio. The amps are read by a remote cable that attaches to the wire near the alternator. Too close and it picks up false magnetic signals.
Of the 6 local shops I feel confident in 4 to test it properly. I understand not all shops deal with modded parts.
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