BajaRunner

Ok I just started a 72 chevy nova project. I need some help on the ignition. No spark. At the coil i have 12 volts on one side, nothing on the other side. Where should I start. I heard that there are external resistors that should bring it down to 6 volts. I dont know anything about these.

I bought a new coil/points and condensor, but want to check on this 6 volt/12 volt thing so i dont burn out the new coil and points.

Where should i start?

JohnJan

You won't have 12 volts on the other side. It goes to the points so that when the points open, the field collapses and the energy is released through the secondary side, the high tension wire to the top of the distributor.

Gimme a call, I'm always messing with my old cars and can probably dig up a wiring diagram. 426-2562

Reed Jensen

Generally old cars with point coil ignition have a "ballast resister" that drops the coil voltage to about 9 volts during running. If you have an additional terminal on your starter selenoid... it bypasses the resister to "up" the voltage during cranking. Actually... since the starter draws so much current... it keeps the coil voltage from dropping so much that the coil won't fire. The wiring is simple. One terminal on the ignition coil will have a " + " sign... THis goes to the ignition (power)... the other terminal goes to the ungrounded side of the points. When the points close... the circuit is complete and the coil charges... When the points open... the field in the coil colapses and discharges through the high tension lead. The big one in the center. The condenser in the distributor acts as a "shock absorber" for the electrical surge so that the points don't arc and burn, and the field colapses totally and not back through the points. Good luck..

Airpacker

If you check for power at the PLUS side of the coil when the points are open, you will see 12v. The resistor only comes into play when the points close completing the circuit and creating a current flow. There is no voltage drop across a resistor unless there is current flow. From what you described, the coil primary winding is open circuited. With B plus on one side and open or disconnected points, there MUST be B plus on the neg side of the coil as well. If not, the windings are open. A quick Balast resistor test is simple. Disconnect the coil from the distributor. Use a test light from ground to the neg side of the coil to create a ground path. Then check voltage at plus side of coil.

Gary Anderson

Wiring made simple.
Keyed ignition "run" position to ballast resistor, then to + coil. You should have 12V when ignition on.
Starter solenoid should have an extra post. Wire this directly to the + coil post.
To check coil, turn key on and ground - post. A spark checker will confirm it works.
- post wired to distributor points.
Set points with feeler guage. Start car. Reset points with dwell meter. Set timing. Note: set the timing only after you set the dwell. Changes in the points will affect timing.
Gary

BajaRunner

I have the 12 volts.

The starter does have an extra post that is NOT connected to anything. do i need to connect that to the + coil?

I am replacing the coil and points/condensor. Not sure if they are good or not, but if I have 12 volts to the one side of the coil, and I hook the + to the extra post on the solenoid i should be good right?

Liberator21

Didn't some of the GM's use a resistance wire instead of a ballast resistor?
Either way, disconnect the (+) lead from the coil, turn on the ignition, and check for voltage on that lead. To get it started real quick, you can take a clip lead from the battery (+) to the coil's (+) terminal, then start the car. That's how we used to take my old man's Rambler for joy rides while he was in work! Just don't run it too long, you could damage the coil.

Gary Anderson

Yes connect the extra starter sloenoid post, marked "S" I think, to the + post of the coil. The car may start without it, but the full 12V really heps get it fired up. It's usually a yellow wire for that connection.
I dont think ballast wires were used past 1969. If it is a ballast wire, it will have cloth around it or it will look silver instead of copper cored.

BajaRunner

You guys are awesome. got it fired up last night!! thanks-

I have never owned an older "muscle car" and always thought that todays technology was much better, and they really werent that fast. well after i fired it up last night i changed my mind. it has the 300hp 327 and this thing freakin moves. It has a 4 speed with a short throw shifter and it burned the tires through each of the 1st 3 gears. (now i need a positract rearend)

Gary Anderson

Got the 350hp 327 in my 68 Vette. Fun, high revving engine. Just keep it in tune, carb included, and they run great.
Gary