wiring help ??

[71_bowtie]

hello, what i'm needing help with is this. have a '78 400 sbc with hei in a '56 chevy 1ton and a '70 chevy pick-up fuse box. aftermarket 4 pin starter switch (bat-acc-ign-start) I can get it started, but then i have to disconect the hei to shut it off. i know the hei needs to be to a switched hot. any help would be awesome, thanks. oh i also read the posts about glass fuel filters-exactly what i have on the '56 and '71 chevy truck projects. i guess i better get em changed. what is the best fuel filter to use? thanks

also have a dietz 112 aftermarket t/s switch with 4 wires (red-black-yellow-blue) Yellow=rt blue=lf i figured that much out. any help on this would be great also thanks again.

[_Ogre]

chances are your getting a back feed into the ignition circuit that can be fixed with a simple diode
i would post this in the electrical section of this forum.
there are some electrical gurus there that might not be looking in the 47-59 threads

[starterman99]

unplug the two wire plug at alternator and see if it will shut off with key switch.If it does you need to install diode in the #1 terminal to block power from feeding back into ignion circuit.

[1project2many]

I usually recommend a relay for the HEI power wire rather than direct wired to the ignition switch. This allows a good power supply to the HEI and will prevent run-on due to current bleed from the alternator. If you decide to use a diode choose one with a high reverse voltage rating as extra insurance. A diode is a one way gate so make sure it's installed to allow current to pass to the alternator. Installed the wrong way, the alternator won't energize properly and the engine will still fail to shut off with the key.

[Russell Ashley]

If you have a three wire (the main wire and a 2 wire plug) alternator try removing the wire from pin 1 in the two wire plug and see if this cures the engine running problem. For a test just temporarily remove the two wire plug from the alternator. Pin 1 is used when the vehicle has a alt warning light and is not needed when the alternator is in a truck with an amp guage, or if you have a volt guage in the truck. If removing the wire from pin 1 cures the problem you can tape it up and leave it off.

[_Ogre]

Originally Posted by 1project2many

I usually recommend a relay for the HEI power wire rather than direct wired to the ignition switch. This allows a good power supply to the HEI and will prevent run-on due to current bleed from the alternator. If you decide to use a diode choose one with a high reverse voltage rating as extra insurance. A diode is a one way gate so make sure it's installed to allow current to pass to the alternator. Installed the wrong way, the alternator won't energize properly and the engine will still fail to shut off with the key.

good idea. i'd go with this

[Russell Ashley]

If you use the ignition wire to pick the relay and don't remove the wire from pin 1 on the alternator, the relay is not going to de-energize and the engine will continue running as before. Why bother buying and installing a diode in a circuit that is not used when you can just remove the wire and be done.
It seems to me that most everyone has a misconception about what pin 1 on a 10Si alternator actually does. If you truck doesn't have an idiot light for the alternator that pin is not used.

[starterman99]

The #1 pin does have a purpose,it is from an ignition source to turn the alternator on at low rpm.It is true most will self energize if you turn them fast enough to create curent in stator winding and there is residual magnetism in the rotor,but if it loses that residual magnetism it will not energize no matter how fast you spin it.All applications have an ignition source to that terminal even when equiped with the gauge package from the factory.

[Russell Ashley]

The alternator is energized by applying battery voltage to pin 2. In vehicles with alt lights the bulb is connected between the ignition switch and pin 1 on the alternator. When the alternator is charging it produces charge voltage on pin 1, which means that the same voltage is applied to both sides of the bulb, causing it to not be lit. If the gauge package mentioned has a volt gauge it could be tapped off from pin one, I don't know. If it has an amp gauge it isn't connected to pin 1 at all.

You can make a 10SI completely one wire with no connections to pin 1 and 2 at all. I believe those are the ones you are referring to that need to be turned fast to energize.

[starterman99]

Originally Posted by Russell Ashley

The alternator is energized by applying battery voltage to pin 2. In vehicles with alt lights the bulb is connected between the ignition switch and pin 1 on the alternator. When the alternator is charging it produces charge voltage on pin 1, which means that the same voltage is applied to both sides of the bulb, causing it to not be lit. If the gauge package mentioned has a volt gauge it could be tapped off from pin one, I don't know. If it has an amp gauge it isn't connected to pin 1 at all.

You can make a 10SI completely one wire with no connections to pin 1 and 2 at all. I believe those are the ones you are referring to that need to be turned fast to energize.

The #2 pin is the voltage sense wire that provides battery voltage to internal regulator.this terminal is constant power and does not go on and off with key.to make a true self exciting 1 wire alternator you change the internal voltage regulatorto a self energizing type.Every automotive application from 1972-on using delco 10SI series alternator has an ignition activation.

[71_bowtie]

thanks for all the helpful tips.

[1project2many]

Starterman sounds like the name of a guy in the alternator / starter reman business. Prolly knows his stuff a helluva lot better than I do.

OEM applications have a connection from pin 1 to ignition power. In a vehicle equipped with factory gauges there's a 2-3 Ohm resistor on the back of the instrument cluster which provides a connection to pin 1. A classic "customer complaint" WRT 10SI alternators sounds a bit like this: "There's something wrong with my charging system. It won't charge after I start it unless I rev it up. But the alternator light isn't on so I know it's not the alternator." The first question an experienced tech asks is "Does the alternator light turn on with the key?" Because if it doesn't, a faulty bulb is probably preventing the alternator from receiving excitation current on pin 1.

Many people tie pin 2 to the alternator stud. This has the effect of forcing alternator output to go to regulator maximum whenever the alternator is spinning fast enough to produce max voltage. GM's intention was for this pin to be connected to the battery separately from the power supply for the rest of the vehicle. The idea was to tie regulator output to battery state of charge to prevent overcharging on the high side or to boost charging when the system is cold. The ignition system voltage was a secondary function when this alternator was designed. There were only a handful of ignition sourced circuits in most cars back then. Electronic ignition was a scary, foreign concept and computer controlled devices belonged in the world of science fiction.

There are replacement regulators which connect pin one and two together and apply switched power to one of the two connections. Using this style regulator provides an internal connection between battery sense and stator exitation. This is not typical for most OEM automotive applications.

I do have low current relays here that might stay energized if connected to the IGN circuit but they are not common automotive parts. A 2-3 Ohm resistor placed between the IGN connection and the relay energizing coil would be enough to force those to shut down with key off. If someone experienced trouble with a power relay staying energized I would suggest adding a ressitor to the relay trigger circuit.

FWIW I have had more trouble with aftermarket performance ignitions staying energized than OEM. The performance ignition system frequently uses the HEI / IGN wire for voltage sense rather than a current supply and power comes from the battery through a separate connection. I've seen IGN voltage as low as 7V cause the aftermarket ignition to operate.

[Russell Ashley]

Originally Posted by starterman99

The #2 pin is the voltage sense wire that provides battery voltage to internal regulator.this terminal is constant power and does not go on and off with key.to make a true self exciting 1 wire alternator you change the internal voltage regulatorto a self energizing type.Every automotive application from 1972-on using delco 10SI series alternator has an ignition activation.

I think you just said the same thing I said.

[1project2many]

Russel, it's not quite the same in regards to initial alternator charging. When the alternator is not turning, power from ignition at terminal 1 provides voltage to the field coil. The field current creates the magnetic field at the armature which generates current in the stator once the alternator begins to turn. Without that connection there is no field current. The reason many alternators will charge without terminal 1 is because the steel armature has been magnetized so many times that it retains a weak residual magnetism. It generates a small current in the stator until the engine's revved up. The stator has a direct connection to the field and terminal 1 and the current created by the armature is fed back to the field coil. This adds to the residual magnetic field and causes the stator to produce more current, which is fed right back to the field coil. The cycle continues until the stator produces enough voltage to trip the regulator.

Terminal 2 is used to control the ground side of the field coil. When terminal 2 voltage raises past the regulator set point the ground connection to the field is broken and the stator output begins to drop. When the T2 voltage drops then ground is restored to the field and charging begins again.

I have run into alternators that won't charge without T1 connected. I specifically remember a low output unit that was added to an old diesel tractor. I want to say it was a Massey, pre-Massey Ferguson, but maybe that's not right. Anyway, the pulley ratios plus the low speed of the engine prevented the alternator from self-exciting. I added an ignition wire to T1 and all was well.

I don't know how you are with electronic schematics but there is a good service manual for the SI alternator online.
http://www.autoelectricservice.net/i..._Technical.pdf