I have spent a good amount of time in the electrical field, and I disagree with some of the things that MAD and others are saying. I'm not disputing their facts (like the warning light, etc), I'm just disputing the conclusions that they draw.
A lot of the reason people are so dead set against 1-wire alternators is that the initial voltage regulators had some problems. There were quite a few of the early ones that failed, causing all kinds of problems. The early ones also had a problem with the self-exciting loop, which lead to a lot of dead batteries and annoyed hot rodders. After including the 1000 rpm sensor, almost all of the problems went away. The new 1000 rpm switch turned on the alternator and kept it on all the time that the engine was running - exactly like the 3 wire. The early ones didn't do this - they would shut down at idle, which caused all the problems. This is why it was initially used in boats and tractors - vehicles that usually didn't operate at idle.
Todays 1-wire alternator are just as reliable as the 3-wire. I've personally had one in my truck for 8 years now, without a single problem. I used it to replace an externally regulated alternator that kept draining my battery (fused contact in the regulator). The 80 amp 1 wire alternator allowed me to eak out life of a dying battery for more than a year.
The interesting thing is that the 1-wire is really exactly the same as a 3-wire. The 1 wire regulator is a 3 wire with basically a rpm switch and a diode added - nothing else. The violent protestations of the people who are pro 1-wire or pro 3-wire is all over absolutely nothing - because it is the same part, just wired slightly different.
The 1-wire is a boon to a majority of guys that have absolutely no desire to understand their wiring harness. I have fixed a countless number of trucks simply because the owner hooked up the wire that turns on the alternator field wrong. Most of them tie it directly to the battery. While that will work, it will quickly drain the battery while the truck is off. Most of them would rather pay $100 or so for a 1-wire than take the time to fix their 3-wire properly. The only thing they lose is the warning light - which most people don't care about anyway.
The MAD article says that 3 wire regulators are better, for 2 reasons.
1. Loss of the alternator light. This one is kind of dumb, because if the alternator isn't charging, you know it almost immediately. Lights dim, stereos stop, starter turns over slow, etc.
2. The alternator isn't turned on with the ignition switch. Once the motor hits 1000 rpm, the functional electrical connection on the alternator is exactly the same as on the 3 wire. No electrical difference.
I don't want flame anybody, but it is obvious to me that this article is based on opinion, not founded on design theory.
