Geo Metro Alternator Circuit Question (for disconnect switch)

[Mr. Previa]

I am currently in the process to put a switch inline with my field circuit wire.

Now, I have a 92 Metro and one wire is B/W and the other is W/R.

I know W/R is for the Lamp and the B/W is for the ignition.

Here is thing problem/oddness.

If I disconnect ONE wire, it doesn't matter which one, the alternator still out puts 14+ volts.

If I disconnect both, then it does not. I find this odd and different from my other alternator mods I have done.

Has anyone experienced this? Before I create a shut off/on circuit for both wires, I want to make sure I am not over looking something.

Thanks.

[MetroMPG]

Afraid I can't help on this one. I never went into the schematics for my Firefly.

You've done this to other cars?

If nobody else chimes in, please come back and post what you learn.

[Mr. Previa]

NP. I have done this before. I am currently running a 2 relay / one switch setup. One relay per circuit.

I think I have a sticky relay, but seems to be a working idea. I still need to tinker on it some more when I get more time. I will be more than happy to post my findings.

[MetroMPG]

You mean you've implemented 2 relays + one switch on the Metro?

Any reason we couldn't just go with a double pole, single throw switch?

[Mr. Previa]

Got it figured out with some help over at the Geo Metro Forum. Alternator Wiring

Apparently it is a self sustaining field. I tested it and sure nuff...

Why not a two pole? Well, just my personal choice I guess. I felt safer with relays, and I couldn't find a "cool" two pole switch that would blend into the dash. I am weird like that...

[Mr. Previa]

The saga continues. Today I was going to start some driving with the alty off. Now, the alty turns on (starts charging) by itself if I give the Geo enough gas. So strange. My fix will be to put another large relay (probably a starter relay) on the positive charge cable going to the battery. That is the last link. (I think...)

[Mr. Previa]

UPDATE.

Ok, here is what I found out about the 3 wire Denso alternators.

The Terminals.

• "IG" goes to the ignition switch, and functions to tell the alternator when to start charging.
• These alternators will start producing current even when just the battery/heavy-duty connector is used.
• "IG" provides power to start the alternator using lower rpms.

This would explain why even though the IG and Lamp circuits are disconnected, the alternator will start charging when I give it a little gas. (increasing the rpm's)

If anyone has any facts to add, please do so.

I hope this will help others when adding a control switch like I did.

My setup is this:

• One 30 amp switch to control 3 relays
• Two, 40 amp relays for the IG and Lamp circuits (yes, overkill, but that is the way I roll)
• One, 100 amp starting solenoid to control the battery charging wire

[Gasoline Fumes]

Good info!

Make sure the starter solenoid is rated for continuous duty. I think Surplus Center - Hydraulics, Engines, Electrical and More has them.