3 Wire Alternator Question, 1971 240z

[510can]

Hey guys,

 

I have a 1971 240z with a 350 in it. The car runs perfect and I love it. Except Iv been having some weird issues with my charging system.

 

Im running the Delco 3 wire alternator the 63amp. And here is how I have it hooked up.

 

Of course the bat wire goes straight to the battery terminal post, the red wire on the plug labeled F#2(Field), and it goes into my post on the starter, I know I could just run a jumper wire from the Bat post to that terminal.

 

The white wire is connected to the post labeled R(#1), and I have it connected with a 3amp diode to a 12v source that doesn't go on until my ignition key is turned on, and the diode is there so I don't get feedback and I can turn my car off with the key again hehe.

 

The problem I have is or Im not even sure that its a problem. Is it seems to me as if the alternator switches on randomly when ever it wants, It definitly turns on when the car goes on, but sometimes when I do night driving my lights dim, and it does seem as if Im running off the battery. At first I thought my connector was loose, so I made sure thats nice and snug. Now on the other hand It might just be me not knowing and lacking knowledge on how a GM alternator is suppose to work, since I own 3 Datsun all with KA's and L series engines hehe.

 

I did have the alternator tested yesterday and it checked out fine. I also have the AMP Meter completely by passed, since I know thats a culprit of all problems since their only 35 amps hehe.

 

NOTE:Due to the size of these pictures, I recommend right clicking and pressing open in new tab or new window.

Edited May 1, 2011 by 510can

[zdlite]

When you ran a wire from the alternator to the battery you effectively bypassed the ammeter anyway.

 

In the original set up for current to get from the alternator to the battery it first had to run into the left side of the fuse box, up through the ammeter, back to the right side of the fuse box then to the battery. If I read what you wrote correctly you have the alternator output hooked directly to the battery. Thus you have all the electrical load flowing backwards from the way it was originally wired.

 

Also the red wire is the voltage sensing wire. Wherever you connect that wire, that is the point where the voltage will be regulated. If you ran it to the main starter lug, that is the same as hooking it to the battery. Thus you are regulating your battery voltage to 14 V, then suffering a voltage drop through the rest of the wiring.

 

I can see why the alternator is confused and your lights are dimmed.

 

If you want the system to regulate properly, you need to hook the voltage sensing wire to somewhere more suitable. I would also NOT connect the alternator output directly to the battery. This link explains why

 

http://www.madelectrical.com/electricaltech/chevymain1.shtml

 

Instead of using a splice like described in the link above, I hooked my alternator output up to a power distribution block up near the radiator. I got it from a car stereo place. It has a 4 gauge lug on one side and 4 fuses on the other. I ran a 4 gauge wire from the alternator to the distribution block. I ran a single 10 gauge wire from one of the fuses to the battery. I replaced the 240 ammeter with a voltmeter from a 280Z, splicing together the big wires that use to hook to the ammeter. I then hooked the two large wires running to the fuse box and ammeter to the second fuse on my distribution block up near the radiator. This way there is no battery charging current running through the dash, and I have two 10 gauge wires feeding the fuse box instead of one. I used a third fuse on the distribution block to power the electric radiator fan.

 

The important thing I did was to run the voltage sensing wire straight to the fuse box (not the starter lug) and the field wire to the charge indicator light on the 280 voltmeter. This way the regulator maintains a constant voltage at my fuse box, not the battery, the voltmeter tells me the health of the alternator and as an added bonus I have a charge idiot light. Everything works perfectly.

 

If you want a quick fix on your set up, try hooking the red wire into the fuse box and not to the starter lug. See what that does.

Edited May 4, 2011 by zdlite

[510can]

Actually I never by passed anything. The red wire you see from the back post is soldered right into the stock white red wire, which runs through the whole car, which ran through the ammeter, and since I had a 63amp on a 45amp ammeter, it fused it self and created a dead short, and was burning up my power cables, and eating the battery. When it comes to wiring I love it.

 

Now once I figured out that this is the 10si 63amp 3wire Delco alt, bells and whistles went off, I just didn't bother posting back lol.

 

Anyways, the white wire you see there is usually hooked up to a dummy light, on the ground side. Except the crazy thing is gm dummy lights are a little bit more than that, and have something like a resistor build into them, or they just used a resisted wire on the plug either way works perfectly fine. Now surprisingly all that does is it turns the alt on as soon as you put your key to IGN ON and nothing else. So on my 240z since I don't have volt meter, nor a dummy light cause they didn't have them from factory. I had to hook up the wire to IGN ON, but with a 10ohm 10watt resistor, alnog with a diode so I don't get feed back.

 

Now the red wire coming from the plug at this point I just jumped to the back post, and the back post I just ran to my battery.

 

Now the car charges with no problems.

 

Now probably due to the fact that Datsun/Nissan always has super fuckin shitty wiring and a weird fuckin way of doing things, everyone will experience these problems in differ ways. So Im probably going to rip the whole harness out of the car this weekend, and just build one from scratch. With how little this car needs, I should save my self about a gazillion wires hehe.

[zdlite]

Maybe I misunderstood you. What I meant was running the main power lug from the alternator to the battery bypassed the ammeter, or at least makes it work backwards from the way it was intended. It also sent all the current for the fuse box through the ammeter. Maybe had something to do with it burning up? Or maybe I still don't understand the hook up.

 

At anyrate glad you are happy.

 

Look into putting a 280 volt meter in. You will get the dummy light that way (BTW, the bulb is what acts as the resistor). It is a simple swap, the 240 front bezel screws right to the 280 back end. Looks dead stock, the 280 fuel gauge works with the 240 sender.