GM Alt. HELP!

[ta TACO]

Here's my deal. I rewired my ignition since it would work properly. Now, I can start the truck with out a problem, but it won't shut off. I had replaced the ignition switch. Since it would not turn off I put the old one back in to see if this would help. NOPE! So I did some research. Made sure the engine was grounded to the firewall, good there. All the wires seem to be good except the Alt wiring. If you look at the pic this shows how it is connected. The only things I forgot to include was the orange wire from the Alt to the Voltage Reg (This wire is not connected to the Alt.) and the solid black wire goes to the solenoid. When I unhooked the alternator I could start and turn off the truck. So it has to be the alternator wiring, right? Can someone please confirm or deny that this is connected correctly or wrongly?



Never mind that little blue line .

[ta TACO]

So I rewired it like this. From what I can find this is correct. Except for the yellow wire to the V/R, not sure about that.

[ta TACO]

OK, let me clarify here, since no one's responding. This is in my 68 f250 C/S with a 390 and a C6. I just really suck at wiring and I did not put this Alt. in.

[The Good Humor Man]

Is this a one wire Gm alt? If so, I believe it has a internal voltage regulator.
Maybe this link might help you out http://www.powermastermotorsports.com/f ... ators.html

[ta TACO]

I believe this is called a 3 wire alternator.

[fitzwell]

first, the diagram you have appears to have the voltage sense wire on the wrong pin on the regulator. The # 1 pin,closest to the charge post, is the exciter wire (ignition switched),the # 2 pin goes to the charge post.

Disconnect the regulator connecton, fire the vehicle up & turn the key off. If that takes care of it,you'll need to install a diode in line on the exciter wire. Radio shack # 276-1661. Stripe on the diode goes to the alt.

[formulaic]

Anyone feel free to correct me if I'm wrong, but the truck turns itself off by stopping voltage to the igntion coil.

Coil gets voltage from two places:
1. the resistor wire running to the ignition switch
2. the "I" terminal of the solenoid (supposedly only when starting)

My trouble shooting would start at the solenoid, since that's the one most likely to be poorly wired to the alternator.

Possible steps for trouble shooting:
1. Start truck.
2. Disconnect "I" terminal on the solenoid.
3. Turn ignition to off.
4. Measure voltage at "I" terminal.
5. Measure voltage of wire that was connected to "I" terminal.

If the truck stopped at step 3, your solenoid is wired wrong/messed up.
If the voltage at the "I" terminal is not zero, your solenoid is wired wrong/messed up. (Though your truck should've stopped.)
If the voltage at the "I" wire is 10 or less, your resistor wire still has power on the ignition switch side for some reason.
If the voltage at the "I" wire is 12, your "I" wire has a short somewhere, or your coil is improperly wired.

[formulaic]

If I had to guess, without any further infromation, I'd guess the alternator is connected to the starter side of the solenoid rather than the battery side. (Which would feed back to the I post, and thus to the coil.)

[seattle67]

Go ahead and disconnect that yellow wire that goes to the old external regulator, the old regulator should be completely disconnected.

Go ahead and try this, unplug the two smaller wires from the alternator completely, including the small wire you have jumpered to the alternator "Bat" post. Try running it with just the large black battery cable connected to the alternator, it should charge fine with the two small wires completely disconnected. If that works, go ahead and plug the small wires back into the alternator (verify that the white wire is indeed going to pin #1 on the alternator), but don't connect the jumper to the "bat" post, see if the "alt" lamp is working now. If it and everything else seems to work then I would leave it like this, the jumper from pin #2 to the "bat" post shouldn't be needed.

Just approach this in a step by step manor and you'll isolate the problem.

Let us know how it goes!

[ta TACO]

Thank you everyone on this. Since I was freaking out and getting pissed . I was looking through everything I could read about this alt. Here is what I have found. Yes, the white and red wire are correct on the alt just not my diagram, sorry. I have disconnected the voltage regulator and unhooked the red sensor wire. I can start and turn off the truck. I cannot figure out where that sensor wire( the red one would go to). Seattle, thank you . You have confirmed what I have hooked up will work. Since the red wire senses how many volt to charge, doesn't it need to be connected somewhere? If it's not hooked up will it just run the 65 amp constantly?

[Thunderfoot]

Davin,

I humbly apologize I thought you had it all worked out... After re-reading I see you still had questions, my head is not as clear as it should be and the 2 noncontributory posters side tracked my train of thought. (we're trying to curb that behavior in the technical forums) I deleted there posts from the thread and unlock it. Your post has every right to be asked and answered here as others run into the same thing or may want to change theirs to the same setup. You were getting very good advice on it.

To add more info;

What you had with both the #1 and #2 wires connected together into the exciter wire was the problem, when the alternator starts charging it puts voltage on the #2 post which in turn was back-feeding voltage to the ignition switch through the exciter wire. The exciter wire is on the same supply circuit as the ignition wire to the coil so it made a voltage loop causing you to not be able to turn the engine off.

You were correct in your diagram of separating the 2 wires on the exciter wire and hooking the #2 post wire to the battery wire. It would be best to hook it up on the starter solenoid with the battery cable there, as it will get a more accurate sense to the regulator and the alternator will charge the battery better.
Here is a diagram that shows the same thing;


And as to the small yellow wire with the fuse, this was part (one of two wires) of the wiring for the Alt gauge, it can be wired back into the circuit but it is easier to just get a voltage gauge and it works much better.

Again I apologize for cutting the thread short.

Shayne

[ta TACO]

Shayne, you say hook the red wire to the solenoid, but that causes the problem to continue. I believe it's called a shunt, but not certain. On the blk wire that connects to the back of the alt, it splits into 4 different wires. Could one of these be causing the problem to continue if I hook up the red wire to the solenoid? Sorry for my ignorance, but electric is not my strong point. I am learning, but sometimes I'm a little slow.

Thank you,

Davin.

[ta TACO]

Oh, I see. So maybe the connector that plugs into the alternator is in backwards. Is this possible? I'll mess with it tomorrow. I was hoping to be driving it tomorrow to work, but that ain't happening.

[Ranchero50]

http://www.stangnet.com/mustang-forums/ ... -info.html

Pretty basic according to this, tie the little red sense wire into the main harness and run the white wire to the idiot light in the dash.

I need to look at my ranchero because this is the same basic wiring for a '80's Ford 65a alternator like the mustangs use. The problem I had and I'm sure you are too is the wiring harnesses are different if you have the idiot light vs. the amp guage. I ended up unplugging my voltage regulator and using that plug as a jumper to get the idiot light from the alternator to the light.

Jamie

[ta TACO]

Thank you very much Rancho50 and Thonderfoot. Somehow the plug has the wires backwards . I guess whoever did the install did this, somehow! I'll mess with it tomorrow. Nothing went right for me today on this beast. Couldn't get the rag joint off the steering box, broke my vise replacing ujoints. Couldn't find a replacement steering shaft since I mangled the treads with a hammer. Had to spend $31 on a tread file. I guess that worked out good. Got the nut to thread back on, but didn't want to spend $30 to fix it. Oh well. Theres always tomorrow I guess.

Davin.