Ballast Resistor, do I have one?

[Starcraft5834]

Ok guys, I got my Mallory Espark conversion kit for my 1987 3.0 140hp, directions say to connect it to ballast resistor.. what's that? do I have one of those in this engine, if so, what does it look like and where is it located? coming off the coil perhaps? I've never seen one before so dont know what Im looking for.. thanks much!

 

[UncleWillie]

Re: Ballast Resistor, do I have one?

The ballast resistor is installed to limit the current to the Ignition/Spark Coil.

Not counting the big High voltage spark wire that goes to the center of the distributor;
You will normally have two smaller wires attached to the sides of the Spark Coil.
One will go below the Distributor Cap the the Points in the Distributor, ;
The other will eventually go to the 12 volts at the Ignition Switch.

The ballast resistor, if you have one, will generally be close to the Spark coil in the wire heading to the 12volts.
The resistor will be a two wire device about the size of your little finger, to larger than your thumb. Lots of variations.

Most modern coils are designed to not need one, or are internal to the coil.

 

[stonyloam]

Re: Ballast Resistor, do I have one?

Should not have a ballast resistor, Mercruiser used a resistance wire instead ( same function). It is the purple wire running from the electric choke to the coil +. Sounds like you just need to hook up to the coil+.

 

[UncleWillie]

Re: Ballast Resistor, do I have one?

Should not have a ballast resistor, Mercruiser used a resistance wire instead ( same function). It is the purple wire running from the electric choke to the coil +. Sounds like you just need to hook up to the coil+.

I forgot about the resistance wire option. I haven't owned a vehicle with points for way too long.

If the instruction call for attaching before the Ballast resistor and you have the Fancy wire;
Treat the wire as the Ballast Resistor and attach before the wire.

Post a picture if you are not sure of what you have.

 

[stonyloam]

Re: Ballast Resistor, do I have one?

Ok guys, I got my Mallory Espark conversion kit for my 1987 3.0 140hp, directions say to connect it to ballast resistor.. what's that?!

Yeah willy, they did not say which end of the resistor did they LOL. If you need the full 12V you would splice in before the choke connector, if the Mallory operates on reduced voltage you can go direct to the coli +. I do not know which the Mallory needs, better check to make sure.

 

[Starcraft5834]

Re: Ballast Resistor, do I have one?

Should not have a ballast resistor, Mercruiser used a resistance wire instead ( same function). It is the purple wire running from the electric choke to the coil +. Sounds like you just need to hook up to the coil+.

Thanks Stony... will take a look, that's likely what I've got going on here.... the directions are pretty clear, just did not understand what that term "resistor" meant or what to look for......

 

[UncleWillie]

Re: Ballast Resistor, do I have one?

Yeah willy, they did not say which end of the resistor did they LOL. If you need the full 12V you would splice in before the choke connector, if the Mallory operates on reduced voltage you can go direct to the coil +. I do not know which the Mallory needs, better check to make sure.

I am confused!
I would think they would not have even mentioned Ballast Resistors if it was meant to attach to the coil side.
Just say "Attach to the Coil", same instructions, resistor or not! ???
If it needs the full 12v, just say so.

Unless, what they really mean is, "Attach it to the side of the coil that does NOT go to the points".
In other words, The ballast resistor side of the coil.

I would like to see the Actual Instructions.

-----------------------------------------------

OK, I found the INSTRUCTIONS. Now it makes some sense. The Ballast resistor is NOT an Option!

WIRING PROCEDURE
IMPORTANT: Make sure that your vehicle is equipped with an ignition ballast resistor (or loom resistance wire) in the wire between the ignition switch and the coil (+) terminal. One easy way to find the ignition ballast resistor is to check the service manual for your vehicle. In general, all vehicles equipped with the Ford/Motorcraft point ignition were equipped with an ignition ballast resistor. If you find your vehicle is not equipped with an ignition ballast resistor, install a Mallory Ignition Ballast Resistor Part No. 700 in series in the wire from the ignition switch. Failure to use an ignition ballast resistor will result in the eventual destruction of the E-SparkTM Ignition Module.

Exception: If your vehicle is equipped with a HYFIRE? Electronic Ignition Control or similar aftermarket ignition control, use ignition ballast resistors and wiring procedures as stated in the instructions for the particular ignition control.

 

[JustJason]

Re: Ballast Resistor, do I have one?

Just measure your voltage at the coils + terminal with the key on engine off. If you do not have a resistor, you should get 11-12 volts. If you do have a resistor, 8 o 9 volts.

If you do have a ballast resistor. The reason why it's there is to keep the points from burning up. It has nothing to do with the actual coil itself. The coil doesn't much care (within reason) what you throw at it. It's just a transformer.

 

[stonyloam]

Re: Ballast Resistor, do I have one?

Hate to be picky here, but just can't help it LOL. The CONDENSER is what keeps the points from burning by absorbing the voltage spike feedback when the coil fires (reducing arcing across the points). The resistor wire limits CURRENT FLOW through the coil when the engine is running, keeping it from overheating. The resistor wire is bypassed during starting so the coil sees full battery voltage when the engine is cranking and battery voltage drops due to current drain by the starter.

 

[UncleWillie]

Re: Ballast Resistor, do I have one?

As long as were getting picky here....

The Condenser keeps the Points from arcing and also forms an LC Circuit with the coil to lengthen the spark.
The Ballast Resistor/Wire prevents excess current from overheating the Coil and/or the Points.

I had an experience with an old Dune Buggy using a Coil that lacked the Ballast Resistor.
The points would overheat and stop making contact ever couple of hours and require re-filing to get home until I replaced the coil with a Non-Ballast coil. Ran fine for 15 years after the replacement.

 

[Lakeshadow]

Re: Ballast Resistor, do I have one?

Hello,

As being a MoPar salty dog in the realm of cars and trucks. Chrysler corporation vehicles of my day had a ballast resistor bolted to the firewall. So being familiar with them I always carried at least two extra at all times. Especially in a boat, a splash of water could crack or break it. On the inside of the porcelain there is a round porcelain piece inside with the wire wound around it to make the resistance. It is normal for the ballast resistor to get quite warm, so mount it not directly on the engine. Depending on how the resistor is made the terminals may wiggle around with the wire wound part that is on the inside. Be careful attaching the terminals, as not to break the porcelain thing inside.

Steady as she goes.....

 

[JustJason]

Re: Ballast Resistor, do I have one?

Hate to be picky here, but just can't help it LOL. The CONDENSER is what keeps the points from burning by absorbing the voltage spike feedback when the coil fires (reducing arcing across the points). The resistor wire limits CURRENT FLOW through the coil when the engine is running, keeping it from overheating.

I'll give you part of that. Except that it has nothing to do limiting current. The current draw is going to be whatever it's going to be regardless of voltage. And current draw has more to do with the intergrity of the ignition system plus the gap on the spark plugs. Not how much voltage you give it. The coil is either going to fire, and draw the current it needs to fire. Or its simply not going to fire, and no voltage flows.

It's the lower voltage that lowers the chance of the points arcing. And prematurely wearing out.

Outboard ignition coils have no problem taking in 100 to 300 VDC and work just fine, without overheating. You can take a 12V ignition coil and feed it 9V when cranking and 14.8 volts when running, it's not going to hurt the coil. When alternators voltage regulators fry, and all of a sudden there is 17 or 18 volts running through everything, coils still work.

 

[stonyloam]

Re: Ballast Resistor, do I have one?

except that it has nothing to do limiting current. The current draw is going to be whatever it's going to be regardless of voltage. And current draw has more to do with the intergrity of the ignition system ......

Ohms law: I= E/R Current (I) = Voltage (E) / Resistance (R), as resistance increases (ie ballast resistor or resistance wire) the current decreases at a given voltage. Eg. 12V / 3 Ohm (coil) = 4 amps, 12V / (3 Ohm (coil) + 2 Ohm (resistance wire)) = 2.4 amps.

 

[Lakeshadow]

Re: Ballast Resistor, do I have one?

Coming about.......

Steady as she goes.....

 

[JustJason]

Re: Ballast Resistor, do I have one?

Ohms law: I= E/R Current (I) = Voltage (E) / Resistance (R), as resistance increases (ie ballast resistor or resistance wire) the current decreases at a given voltage. Eg. 12V / 3 Ohm (coil) = 4 amps, 12V / (3 Ohm (coil) + 2 Ohm (resistance wire)) = 2.4 amps.

I know ohms law. And I know how transformers work as well. Ohms law describes the behavior of voltage through a load. An ignition coil is a step up transformer. A transformer by itself however, is not a load. the resistor wire is a load, but the coil is not. The cap and rotor, the plug wires, and the plug gap (and type) is the load, not the coil.

Your not applying ohms law correctly here, as you are trying to apply ohms law to something that is not a load. If your going to do that, you need to treat each set of windings separately, and you also would need to know your turns/number of winding so you can figure out what the power conservation factor is going to be as well. Which is going to get way to technical for a forum like this. If there are any engineers here maybe they an chime in.

 

[UncleWillie]

Re: Ballast Resistor, do I have one?

I was trying to stay out of this one, but I just can't control myself.....

Ohms law has more to do with it than not.
There is very little Iron in a spark coil, so the Inductance is very low and Resistance dominates.

Lacking significant Iron cores, Ignition coils are low Permeable Transformers, which means the cores become saturated.
Once saturated, the only thing limiting the current is the Resistance of the Primary Winding which is commonly just a few ohms.
The primary winding behaves very similar to a simple Resistive Load.
The Ballast Resistor is there to limit that current.

A good explanation of how the Ignition Coil Actually works can be found HERE.

I was surprised at how much WRONG information you can find on this subject on the Web.
If it's on the Web it must be true. :facepalm:

 

[JustJason]

Re: Ballast Resistor, do I have one?

Let me ask you this 1 question. Is a transformer a resistive load or an inductive load? Which type of load is a transformer?

 

[Maclin]

Re: Ballast Resistor, do I have one?

While there is resistance from the windings that can be measured when static, the load is Inductive when in use.

 

[JustJason]

Re: Ballast Resistor, do I have one?

Correct, inductive.

Now here is why ohms law does not directly apply.

In SM3 for a mercruiser engine the primary resistance in an ignition coil for a coil used on points is .9 of an ohm. Please tell me the current draw at 12V, and then say 8V. All I want to know is the primary. The secondary is a separate circuit.

While your working on that, answer me this as well. Electric motors are also inductive loads. How does ohms law apply to that?

 

[UncleWillie]

Re: Ballast Resistor, do I have one?

Let me ask you this 1 question. Is a transformer a resistive load or an inductive load? Which type of load is a transformer?

It is Both. The windings have both a resistance and an inductance.
When you think the word "Transformer" The common Power Converting Transformer is what comes to mind.
It will have more than enough Iron in the core and enough permeability that the core will never saturate at the frequency it is design for.
The Inductance in the common Transformer, under normal operating condition, is the dominating factor.
The resistance is still there but can normally be ignored.

This is an important consideration when you attempt to operate equipment designed for 60hz, on 50hz power mains.
The 60hz cores may saturate and the transformer primaries will over current and overheat.

The Ignition/Spark coil is a low permeability transformer and is operating on DC not AC.
The points close, the Inductance in the core limits the current Just like a normal transformer until the core reaches saturation.
The current then becomes steady state DC and is limited only by the Resistance in the windings.
The points Open, The collapsing magnetic field attempts to keep the current flowing and charges the capacitor.
Once the Cap reaches max charge, the current reverses and the spark happens.

This is NOT a simple AC transformer circuit.
Look at the link in Post #16 again.