alternator question

[wilson_wwsc]

I want to install a higher amperage alternator in my 1973 240z. I am planning on getting a 105amp GM 3 wire internally regulated alternator. I know that the factory harness cannot handle the extra amps. Would it work if I connected the factory harness wire that is currently connected to "a" on the factory alternator to the battery charging terminal to the new alternator and add a wire from the charging post of the new alt. straight to the battery? Where would the factory wire connected to "e" on the fact. alternator go? And do I just insulate the F and N wires?

[FastWoman]

Well, if you do that, your ammeter won't work. I don't know if that's a problem to you.

You should also have a maxifuse or fusible link somewhere in the line between the alternator and the battery.

If you want to keep your ammeter intact, you might consider disconnecting it and removing the shunt from the back. Then drill a hole through the shunt that is positioned maybe 40% of the distance between the two holes. Remove the black wire from the A post, and substitute your heavier wire (capable of carrying maybe 120A -- automotive standards, not household) from the A post to a mounting block where you are to relocate the ammeter shunt. Connect the heavy wire to the hole you drilled, and connect the closer end of the shunt to a 120A maxifuse (or 120A fusible link). Connect the other end of the maxifuse to the battery. Now run small gauge wire from both sides of the shunt to both sides of the ammeter. Your ammeter will no longer be as sensitive and will peak at full scale at hopefully around 105A. It also won't show system discharge, unless perhaps it's through a shorted alternator.

Edited December 14, 2010 by FastWoman

[Zed Head]

I was going to paste a link to a thread at Hybridz that would help you out but see that you are already there. Did you read Post #17? The amps only matter if you add new loads to the harness.

http://forums.hybridz.org/index.php/topic/96568-alternator-question/

I hope that you're using one of these. If that's the stock 73 alternator (I can't tell) then you'll have an external voltage regulator to deal with. Do that, then just add a wire to a junction point for the charge wire to connect to and wire all of your new loads to that. Edit #2 - this is listed for the 60 amp upgrade but it will probably handle your 105 amp alt. Zsondabrain would know for sure. Either way, the 105 amp alt. is not a drop-in swap.

http://www.thezstore.com/page/TZS/PROD/12-4068

The ammeter vs. voltmeter issues discussed in the Hybridz thread are a whole different problem.

edit - Dang, FW and cozye are fast. FW, the above was written as you posted...

Edited December 14, 2010 by Zed Head

[FastWoman]

That's why they call me Fast Woman! Actually I just have a time advantage over you and Coz, because I'm on the East Coast.

[FastWoman]

Ah, well, considering post #17, if you relocate that secondary wire from the starter post to the alternator-side of the shunt (as I've described the above circuit), then your ammeter will show system discharge too. :-)

[Zed Head]

That other thread was so long that I forgot that Wilson started it! Oops. I guess he's looking for a new perspective, I thought Mr. Hines gave some good advice.

Wilson, is that 240Z alternator rigged on to your small block chevy? Then you do have the external regulator to deal with, unless someone has already swapped a modern alt. in. Or you might need that plug or you can try the Atlanticz rewiring.

You mentioned headlights though, so you'll probably need a relay to take those off the factory harness.

[wilson_wwsc]

Thanks for the QUICK responses! I do have relays running the headlights and the fan. The regulator is still there, but the alternators I'm looking at would have an internal volt. reg. I really don't care if the ammeter functions. I'm going to see how hard it is to reach the wiring needed to make it work.

[steve91tt]

On a 1973 you also need to be careful to see that you don't have a fuel pump relay that will be left permanently on by switching to an upgraded alternator. See link...

http://www.classiczcars.com/forums/showthread.php? t=39259

I have a 1973 and have run a wire directly from the alternator through a fuse to my battery. It works great. The ammeter does not work but I think it's better to have as little current under the dash as possible. I also disconnected the fuel pump relay and run mechanical only.

Edited December 14, 2010 by steve91tt

[wilson_wwsc]

Ok, so running a wire directly from the alt to the + terminal on the batt would keep less current on the factory harness than no wire from the alt to the batt, correct? Path of least resistance going on here? I should have paid more attention to circuits in physics.

[wilson_wwsc]

Assuming the alt i have right now is the stock unit, or stock replacement, what does the terminal on the far left, labeled "E" do? Is it where all the negative wires from lights and such go?

[FastWoman]

Yes, another wire, providing another current path, would offload current from the main harness, provided your connections are good. If I were you, though, I'd go ahead and abandon the wire from the A post. Why? Well, what would happen if the connection were lost on your new wire, perhaps because you forgot to connect it one day? Then you'd be sending 105A through the harness wiring. KISS is always best.

I think the "E" is probably an "F," probably for "field." I believe it's energized by your voltage regulator. When it's energized, your alternator puts out. There are differences in the wiring of external and internal regulator systems, and I regret I don't really know the differences that well. I think Dave's your guy (Z's Ondabrain) for this one. I think you need a diode on the field coil to prevent backfeed to your system when upgrading to an internally regulated alternator. Otherwise you won't be able to kill the ignition! There's probably plenty of info out there (e.g. Atlantic Z) about how to do the conversion. Simple mod.

[wilson_wwsc]

I agree KISS is good. I go KISS with firearms too. =)

According to wiring diagrams, the left most post is E and the on of two terminals in the black part is F.

http://forums.hybridz.org/index.php/gallery/image/3169-240z-wiring-diagram/

I still need to figure out which wires I need to keep wired up with a new alternator to keep the car functioning.

Thanks for all the help so far. I am piecing this together slowly.