Alternator and voltmeter question

I have installed a new Delco SI alternator and I have a question about the the readings I'm getting at the voltmeter. By the way - I've done a search and read about the differrent ways to wire the one-wire alternator, so I'll tell you how I have mine wired (for now) until you guys tell me different.

I have a new Optima red top battery.
I have a new 100 amp alternator with BAT post wired directly to the battery w/ an 8 ga. wire.
I have the #1 wire going to the ignition switch w/ a warning light in line.
I have the #2 wire going to the positive wire of my electric fan.
I have the voltmeter + post connected to an ignition switched 12v source on my fuse block.

So here's what happens: With the engine on and at idle (with fan off), the warning light is on and the voltmeter shows about 13v. When I switch the fan on the voltmeter jumps up to about 15v and the warning light goes off. I'm assuming this is because the #2 wire is sensing the voltage drop from the fan being on so the alternator pumps up the output to compensate and thus puts out more and sends more voltage through the system.

One weird thing. When I pulled the positive cable off the batery, the engine dies. I was expecting it to keep running. :?

Does that sound right? I wired it that way because I wanted to make sure I have a way to trigger the alternator to charge the battery and since I run only the elec. fan (no fan off the belt), the fan will always be on.
Thanks.

 

I tie terminal 1 thru an idiot lamp to switched ignition, terminal 2 thru a fusible link to the starter (+) terminal, and the BATT terminal thru a larger fusible link directly to the battery. I don't follow the fan idea, but in any case the engine should still run with the battery terminal pulled if the alternator is working, even though it's not such a hot idea to do that. If you mean it won't run with the fan off, when you're supplying no field excitation voltage, then that makes sense.

 

I just pulled the + cable off the battery to see if it would keep running or not - and it didn't. I don't really know what that means.

I don't know if having the #2 wire going to the electric fan is a good idea or not. I just thought that since it's my biggest constant pull of power it would be a good place to put the sensor - but it's making the alternator pump the system up to 15v or even higher.

 

The fan shouldn't be hooked up like that. Run the fan through the fuse block, or if there isn't room, from the battery through an inline fuse or breaker through a heavy duty toggle switch (or relay if you know how to wire it). Also, if your alternator is designed to be a one-wire unit (I think I read that right) it should be self exciting once you rev the engine a bit.

 

What it means, is that your ignition is running off the battery only, when your #2 wire is getting no power. Your 15V output is probably due to the load drop at the fan power feed. I would connect it at the starter (+) terminal, or to the battery - either way thru a fus. link.

I've found that even the "1 wire" alternators will put out better at idle, if the field terminal is hooked up.

 

I guess I should clarify the wiring to the electric fan. It currently does get power from the the battery, via a distribution post on my firewall and through a toggle switch, it's just that I have also tied into that + wire near the fan with #2 alternator wire for sensing purposes. I'm just winging it based on a compilation of things I've read in the past, so different (better) ideas are of course welcome.

If the alternator is self exciting- that's great, but what then is the purpose of the #2 wire?

Sounds like I could just connect the #2 to the starter + terminal and leave it that, but there's also the widespread opinion that the #2 wire could / should be wired as a jumper to the alternator BATT post. I was trying to take it one step further by sensing at my biggest power draw.

Mostly trying to figure out:
1) if how I have it is wrong- so I don't screw something up and
2) why it is wrong - so I can learn something

Thanks, Mike