# Ballast resistor

• posted

Hello all. First time poster to the newsgroup.

I have a question about a ballast resistor. Would the ballast resistor pictured here,

(an automotive ignition resistor) reduce voltage in an open circuit, a closed circuit, or both? If it had 12v input and I connected a voltmeter to the output side, with nothing else connected to it, would it read 12 volts or a reduced voltage.

Here is a statement I read:

Basic electrical thing: You always read full voltage on an open circuit.

Is this still true if there is a ballast resistor in the circuit? It doesn't seem like it would be to me but I'm no electrical guru.

Thanks for any assistance you can offer?

Leon

• posted

Actually, sci.electronics.basics would have been more appropriate.

Ohm's Law: E = I / R

In words: The voltage drop across the resistor is directly proportion to the current flowing thru it.

• posted

E = I R (Product--not quotient.)

• posted

That's better, I was about to scream at you!!

And better yet, for the poster, E means the Voltage that you asked about. Definitely the voltage will drop, but it depends on your target load (distributor), your Ballast Resistor is part of the load...... Heeheee.......Donchaknow............

• posted

You misundertand, you can't test it on a stand-alone unit. It has to be installed with your distributor to reduce the current/energy going to your distributor. The question is why do you think you need Ballast R? They claim it will reduce misfiring, that's their claim, it may not be the cause. Find the root cause of your problem first, ask yourself Did anyone adjust your spark plug too close? If Yes, then that's where your problem is, you wouldn't need Ba R.

Yes it will reduce the energy going to your Distributor. Bad idea, too, your car will sucks lots of gas and will be weaker.

Jack

• posted

Something else I want to throw in, if you had a dragging brake, that maybe the cause of your engine getting too hot, when engine is too hot, misfiring can occur.

Jack

• posted

The bit that's nagging at you might be explained thus: the meter itself has resistance as well. Putting the meter in series with the ballast resistor would form a voltage divider, which one would think would put some voltage across the meter and some across the ballast. It does in fact. But the ballast, if okay, is only a few ohms, while a typical digital meter is ten million ohms; so the meter will get 99.99+% of the voltage, which is close enough for the measurement you want to make.

```--
God help us all.
Because we're down to PIAPS, B. Hussein or McStain,```
• posted

Jakthehammer wrote:

This assumes that the OP is dealing with a modern system.

Here's my understanding of the way this worked:

For decades, the traditional (Kettering) ignition system would drive the hell out of the igition coil during the few second of *cranking*. After the engine caught, the ballast would be inserted into the primary circuit and *that* current would be enough to *run* the thing.

Bypassing the ballast permanantly and running the ignition system at cranking power *all the time* would shorten the life of the ignition coil (and points).

• posted

yes. the ballast resistor was shorted out to compensate for the lover available voltage while starting an engine. It wasn't needed with a new battery, and a warm engine, but in cold climates the voltage available to the coil could sag to 6 volts. The standard ignition coil is a 6 volt coil, and used wth the ballast to use it at 12 volts.

It will damage the insulation on the plug wires, as well.

```--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.```
• posted

Hey man, sorry to say you assumed wrongly. Ballast has never installed in a car by the modern carmaker. They made the ignition coil correctly without the need of B.R., only when you want to buy the alternative ignition coil to replace the OEM part, sometimes the alternative could be too hot or excessive for the car. That's why the maker of Ballast Resistor recommended reducing the power for the alternative Ignition coil.

• posted

The resistance in a meter is 0.01 ohm, not to worry about. You can always subtract it off your reading.

People don't put a volt meter in series with a circuit, only in Amp reading mode.

• posted

The resistor will only drop a voltage if there is current going through it.

The ballast resistor reduces the voltage in normal running of the engine.

While the engine is being turned over the battery voltage drops a few volts so the ballast resistor is shorted out to make up for this.

• posted

I was trained that the ballast resistor is bypassed during start because the coil needs the full voltage to generate a very hot spark to get the ignition started. If the coil did not have the ballast in line during normal operation it would overheat and fail.

- Tim -

• posted

there's two things wrong with that training.

Yes the ballast by pastes during starting how ever, this is due to load on the battery during turning over in cold conditions. The battery is not as full of life at cold temps and does drop the voltage either way when turning over the engine.

The coil must operate at the correct voltage for long term operation to prevent over heated spark and miss timing.. both you do not want.

The ballast also served as a noise canceling device for your car's electronics. It was normally mounted on the firewall in a carefully designed mount that extracted heat and help keep noise from the points from traveling around the mounted structure..

```--
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• posted

Maybe true for older technology.

• posted

Makes sense but this sounds like it's happening in American cars. Japanese cars don't use Ballast or any thing like this.

• posted

Thanks for all the replies. In my case the ballast resistor reduces the voltage to the coil and distributor points. If the ballast resistor is removed the points will burn and cease to function. The circuit through the starter solenoid provides 12 volts when it is engaged during starting. After the vehicle has started the ignition circuit provides

6-8 volts through the resistor.

Leon

Le> Hello all. First time poster to the newsgroup.

• posted

Who wants a Japanese car? Give me old, American built iron, any day.

```--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.```

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