Ballast resistors/wires?

[Boomyal]

Can/do these ever go bad to the extent that they begin to pass full voltage? I assume that most older point/condensor powered autos had them?<br /><br />My '65 Mustang Manual says that there is one and that seems consistant with the way the positive lead to the coil was run. It came out of a wiring loom direct to the coil. The manual showed that the tie in from the full voltage supply from the starter solenoid occured further back in the loom.<br /><br /><br />Pertronix recommends that you bypass any ballast to give full voltage to the coil. So once the system was hooked up and running I checked the voltage at the coil and it was a full 12.5 +-.<br /><br />What would have been the symptoms if the points had been getting full voltage all along?

 

[LubeDude]

Re: Ballast resistors/wires?

Originally posted by Boomyal:<br />[QBWhat would have been the symptoms if the points had been getting full voltage all along? [/QB]

You would have burned the points up.

 

[levittownnick]

Re: Ballast resistors/wires?

Symptoms? Good question. I doubt that the resistance could ever fail in a way to give full voltage. The normal failure is open (No voltage). These systems had a by-pass usually located on the starter solenoid. The by-pass shorted the resistance wire during cranking so that the coil input got a boost in voltage to compensate for the drop in voltage during the high current drain during starting. <br />The nominal coil input voltage was about 9 volts, which was derived from the battery through a resistor (or resistance wire). When cranking, the battery drops down to about 10 volts. When cranking, bypassing the resistance puts full battery voltage on the coil so that the coil High Voltage output is suficcent for ignition. When the starter solenoid is released, the nominal battery voltage & coil voltage is restored. Note that the coil output voltage is directly related to it's input voltage (a 20% drop on the input voltage results in the same % drop on the output. This could make it hard starting.)<br />The classic symptom of an open resistance is that during cranking, the engine starts, but as soon as the key is released, the engine stalls.

 

[levittownnick]

Re: Ballast resistors/wires?

Symptoms? Good question. I doubt that the resistance could ever fail in a way to give full voltage. The normal failure is open (No voltage). These systems had a by-pass usually located on the starter solenoid. The by-pass shorted the resistance wire during cranking so that the coil input got a boost in voltage to compensate for the drop in voltage during the high current drain during starting. <br />The nominal coil input voltage was about 9 volts, which was derived from the battery through a resistor (or resistance wire). When cranking, the battery drops down to about 10 volts. When cranking, bypassing the resistance puts full battery voltage on the coil so that the coil High Voltage output is suficcent for ignition. When the starter solenoid is released, the nominal battery voltage & coil voltage is restored. Note that the coil output voltage is directly related to it's input voltage (a 20% drop on the input voltage results in the same % drop on the output. This could make it hard starting.)<br />The classic symptom of an open resistance is that during cranking, the engine starts, but as soon as the key is released, the engine stalls.

 

[DJ]

Re: Ballast resistors/wires?

You would have burned the points up. <br /><br />

Not to mention, overheating coils.

 

[Boomyal]

Re: Ballast resistors/wires?

Originally posted by DJ:<br />

You would have burned the points up. <br /><br />

Not to mention, overheating coils.

I hope not DJ. 'cause this coil, which looks OEM or equiv, (approx 1.5 ohms resistance) is/has been getting the full meal deal. And it apparently has been based on my voltage reading before and after starting.<br /><br />Full voltage is ok in my mind because Pertronix likes it that way. I just wonder what happened to the ballast resistor/wire. It's not the kind of situation that someone woulf have purposely eliminated.

 

[TELMANMN]

Re: Ballast resistors/wires?

A resistor in the primary ignition circuit that lowers voltage after the engine is started to reduce wear on ignition components.<br /> A resistor is either open or shorted. It can reduce its resistance over the years but then it will fail as above.

 

[Dunaruna]

Re: Ballast resistors/wires?

1.5 ohm coils handle battery voltage easily. 3.0 ohm coils can overheat and boil the oil - that's why epoxy filled coils are used more and more these days.

 

[Boomyal]

Re: Ballast resistors/wires?

Originally posted by Dunaruna:<br /> 1.5 ohm coils handle battery voltage easily. 3.0 ohm coils can overheat and boil the oil - that's why epoxy filled coils are used more and more these days.

I'm assuming that's what my coil is. That is what my manual said anyway. I think specifically, "1.3 to 1.7 ohm".<br /><br />That's also interesting Aldo because Pertronix says that you can eliminate the ballast resistor on coils of .6 ohm and higher. <br /><br />What determines the ohm rating of coils that are chosen for specific applications?

 

[KRS]

Re: Ballast resistors/wires?

The ballast resistor (a coil of wire) may have been shorted out by a metal object or the coiled wires are pushed together... and that would make it ineffectual.

 

[Dunaruna]

Re: Ballast resistors/wires?

Originally posted by Boomyal:<br />

What determines the ohm rating of coils that are chosen for specific applications?

An ignition coil has two distinct windings - primary and secondary. The OHM rating is reffering to the primary winding. A 1.5 ohm primary winding will produce (roughly) 500 volts, a 3 ohm primary winding will produce about 300 volts. As the voltage passes through the secondary windings, it increases 100 fold. As you can see, a 1.5ohm coil is capable of about 20,000v more at the business end of the circuit. But there is a problem, you can't use a 1.5 with points because you would be changing them every half hour, you would turn your distributor into and arc welder. So for points (and early 'dumb' electronics), 3 ohm coils feed with 9 volts (ballast resistor) was the only way to save points. <br /><br />Another reason for 3ohm coils and resistors was to help reduce heat in the coil. <br /><br />Modern manufacturing techniques (with coils) & the introduction of 'smart' electronics allow for the elimination of the ballast resistor. Higher voltages are now possible and the switching mechanism is much quicker and finely controlled. In fact, some car manufacturers are playing around with the idea of 36volt systems.<br /><br />This all leads to one thing - BIGGER spark. In the not so distant future, 0.5 ohm coils will be the norm.IMO.<br /> <br />I find it interesting that a similar senario is currently being played out in the audio industry, manufacturing techniques are allowing lower OHM speakers and amps to be built. some down to 1 ohm, this allows the amp to feed the speakers with more juice.<br /><br />Aldo

 

[Boomyal]

Re: Ballast resistors/wires?

You'll like this Aldo. Discovered on my boat today that I had the connections on my boat coil reversed. Positive Pertronix lead to negative coil terminal. Negative Pertronix leat to positive coil terminal. Negative tack lead to positive coil terminal. Positive battery lead to negative coil terminal.<br /><br />Hey! it ran? and didn't make any noise!

 

[Dunaruna]

Re: Ballast resistors/wires?

I know with points, it doesn't cause damage. Not sure with a module though.<br /><br />Hey, the 'prince of darkness' did it (lucas), why not you.<br /><br />The primary ignition circuit starts at the batt and finishes at the batt. The electrons were flowing in the opposite direction, but they were flowing.<br /><br />Burns out spark plugs a lot quicker though.

 

[Boomyal]

Re: Ballast resistors/wires?

Fortunately I didn't have more than 45 minutes +- run time on the whole program. Hope no damage was done. The tach did act goofy while I was cranking the motor but would even out once running. Now it seems to work normal.