Ballast resistor Q's

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Justin_Day

Justin_Day

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I used the search function and read about 50 threads and did not find any with my exact problem.

I have replaced the coil, rewired the ignition, replaced ICM, New plugs, New wires, just upgraded to an electronic dizzy all within the last 150mi

I replaced the 4 prong Balance resistor about 900 miles ago.

When the car is cold it fires first turn, stays running and runs like a champ as long as I don't shut it off. It is fine if I drive all day long if I don't shut it off. BUT, once it is up to running temp, or driving for 5-10 minutes and I shut it down....

It still fires immediately on the starter. But as soon as I let off the key it falls on its face and dies the second I let go of the key. If I let the car sit for 20 minutes or so it will fire up properly again.

Is this a sign of a bad/dying BR or something different?
 
First thing I'd try is warm it up and try to get the problem to "show." Then hook a voltmeter to the coil+ and see what it reads. If you lose coil + voltage it's VERY likely a defective ballast.

Make CERTAIN you have the ballast wired correctly. Also determine if your box is a 4 or 5 pin box. You cannot tell by looking, because many 4 pin boxes still have the unused 5th pin. You must use an ohmeter from the pin to see if it's a dummy

The difference:

'4 pin'

Ignition_System_4pin.jpg


Ignition_System_5pin.jpg


Look at the ballast..........it has a "U" cutout at one end. This indexes the ballast so that the correct "side" is hooked to the coil. In reality, the coil resistance of either a 2 or 4 pin resistor is NO DIFFERENT in wiring than an old points resistor.

Ballast_Resistors.png
 
Yes, it has the cut out at one end. I wired the ballast, coil, and 4 pin ICM based on a diagram I found on here I will double check with it when I run outside in a few minutes. I guess I just assumed it wouldn't run at all if I had messed up any of the wires.

I will borrow a friends voltmeter, or I guess since they are cheap enough just grab another BR to see if it makes a difference until I can grab the tool.

Thanks for the quick response!
 
Alright, I went out and checked over everything. I had some kind of mix between those two I was running the four post resistor with a 4 pin control module for basically no reason.

I switched it to a two post and switched a few wires to what your 4pin module schematic shows.

It fired right up and is running great.
 
sooo .... you are running an electronic ignition now. I assume you went with a 12v coil ? if so, why not just delete the ballast and completely remove it from the system ? ..
 
65-440 said:
sooo .... you are running an electronic ignition now. I assume you went with a 12v coil ? if so, why not just delete the ballast and completely remove it from the system ? ..
Click to expand...

??????????????
 
67Dart273 said:
??????????????
Click to expand...

What I was getting at is if he thinks the ballast is his issue, and he's no longer running the older style coil / points why not delete the ballast. It would serve no purpose at that point and removing it would take it out of the equation.
 
the ballast prevents the coil from overheating at low engine speeds ,it is necessary ,dont remove it! unless you go to a e-coil .
 
Ballast resistors were originally intended to cut voltage to points so they would not burn up as quickly.

Each time I say that I get the "no, yer wrong" comments.

But I digress.
 
teringer said:
the ballast prevents the coil from overheating at low engine speeds ,it is necessary ,dont remove it! unless you go to a e-coil .
Click to expand...

Not correct about E-core..

E-Core coils typically have half the primary resistance of a typical can coil. They will build more current, and more heat. E-core coils are potted, not oil filled so they can actually fail sooner. E-core advantage is less loss in magnetic circuit, from slug design of can, to a controlled air gap, reducing magnetic path.

Using a HEI ignition module that limits the current to a safe value by hardware and predictive dwell time control, will reduce coil temperature and result in a more efficient ignition.
 
Justin_Day said:
... just upgraded to an electronic dizzy ...
Click to expand...
I think the confusion is that we don't know what dizzy you have. If the 1975 car in your sig, then it already had electronic dizzy, so what is this "upgrade"?

I too suspect your problem will return. Since it sometimes worked before, your ballast probably wasn't broken (normal problem for "dies when I move from crank to run"). Putting in the replacement surely wiggled some wires. I would suspect the feed-thru terminals in the bulkhead connector (any melted plastic?), the ignition switch, or seat-belt interlock (your year?).

Bad Sport, I agree with your statement. The ballasts also protected the coil and ECU in the early Mopar electronic ignition. As Kit said, HEI controllers have smart electronics to control the coil current and thus don't need a ballast. Mopar did that too, but buried in their "spark computer", so hard to leverage for a retrofit (plus those were temperamental), and now inside the engine controller (PCM).
 
Bad Sport said:
Ballast resistors were originally intended to cut voltage to points so they would not burn up as quickly.

Each time I say that I get the "no, yer wrong" comments.

But I digress.
Click to expand...


The thing is you are "sorta" right. That is not why, per se. "Everybody" could have easily designed a coil to operate directly off 12 (14) volts. The REASON that GM, Ford, Chrysler and AMC used a ballast with a lower voltage coil is "so that they could bypass the ballast" during start and MAINTAIN a good hot starting spark. THAT is the key

An HEI (GM) and just about any coil tho, has enough "extra" spark (even a stock coil) that this bypass is not needed.
 
65-440 said:
What I was getting at is if he thinks the ballast is his issue, and he's no longer running the older style coil / points why not delete the ballast. It would serve no purpose at that point and removing it would take it out of the equation.
Click to expand...

Sorry, but depending on what ignition he's running, this STILL is not correct. If you run a factory - like Mopar electronic, a ballast is required.
 
I’ve been doing some research on this very subject for my own education for reasons unrelated to this thread. From the 1973 Factory Service Manual (FSM), in reference to the dual ballast resistor using electronic ignition, (note: the compensating side of the dual ballast resistor is the side that is in series with the coil positive): “The compensating resistance serves the same purpose as in the contact [points] ignition system, that is to maintain constant primary current with variation in engine speed. During starting this resistance is bypassed, applying full battery voltage to the ignition coil…”

Here are a few more useful specs from the FSM:

Coil (Essex 2444211)
- Primary Resistance: 1.41 to 1.55 ohms
- Secondary Resistance: 8000 to 10200 ohms

Ballast Resistor (resistance @ 70F-80F)
- Compensating side (coil side): .50-.60 ohms
- Auxiliary(control side) (note: not used with 4-pin ECU): 4.75-5.75 ohms

Current Draw (Coil and Ballast Resistor in circuit)
- Engine stopped: 3 amps
- Engine idling: 1.9 amps

What I have learned from reading various sources is that the Coil, the Ballast Resistor (or no ballast resistor) and the ECU must all be considered when selecting components. As others have said, some ECUs (for example HEI) have an internal current limiting circuit so they do not need a ballast resistor. If the manufacturer calls for a ballast resistor (Mopar and others) it is there to maintain an acceptable current level for the coil so it does not overheat (and to allow hotter spark for starting). One last point, race only vehicles and street driven vehicles have different requirements, so don’t get all twisted.

I know of one article on the web from Mopar Muscle that states if you have electronic ignition you can remove the Ballast resistor because they are there for points distributors. In my opinion that is a very misleading statement.
 
I have explained this in another post, but here it is again.The function of the ballast
resistor is to compensate for hi CURRENT demand at idle and lower engine speeds.
This is caused by the longer actual dwell time the coil primary windings are subjected
to at low speeds,i.e. 30 degrees at 900 rpm lasts 4 times as long as it does at 3600
rpm,thus the saturation time is enuff to create excess heat. Since the coil has to be
engineered to saturate quickly enuff and deliver sufficient energy at the maximum
design rpm,the ballast provides the needed flexibility allowing low speed operation
by providing resistance that increases w its own temp increase at those same high
demand conditions.This reduces the the voltage and thus temp of the coil,keeping
it alive and also saving the points and EI transistors,whichever you're running.
ALL systems that deliver 12V to the coil,and fire it by providing a ground then
removing it need a ballast GM,Ford,Mopar,Ferrari,..it doesnt matter.The methods
are different,(GM ballast wire,Ford inline moulded plasticesque unit),but the need
and functions are the same.This includes Mallory unilite,Prestolite,points,Mopars
oem EI,etc..Obviously starting drops system voltage to approx. 10.5 while crank-
ing,so they all have "bypass"methods to ensure sufficient spark energy.
MSD and other discharge type systems don't use the saturation method,instead
they they "bombard" the coil primary w/100's of volts multiple times w/capacitor
discharges,thus no heavy current draw except thru the ign unit itself,which is
designed for this purpose,thus no ballast at the coil needed.:coffee2:
 
Make sure you use a few spacers/washers on the back of the ballast to space it away from the firewall. This will allow it to run cooler and posibly last longer.
 
Killer6 said:
I have explained this in another post, but here it is again.The function of the ballast
resistor is to compensate for hi CURRENT demand at idle and lower engine speeds.
This is caused by the longer actual dwell time the coil primary windings are subjected
to at low speeds,i.e. 30 degrees at 900 rpm lasts 4 times as long as it does at 3600
rpm,thus the saturation time is enuff to create excess heat. Since the coil has to be
engineered to saturate quickly enuff and deliver sufficient energy at the maximum
design rpm,the ballast provides the needed flexibility allowing low speed operation
by providing resistance that increases w its own temp increase at those same high
demand conditions.This reduces the the voltage and thus temp of the coil,keeping
it alive and also saving the points and EI transistors,whichever you're running.
ALL systems that deliver 12V to the coil,and fire it by providing a ground then
removing it need a ballast GM,Ford,Mopar,Ferrari,..it doesnt matter.The methods
are different,(GM ballast wire,Ford inline moulded plasticesque unit),but the need
and functions are the same.This includes Mallory unilite,Prestolite,points,Mopars
oem EI,etc..Obviously starting drops system voltage to approx. 10.5 while crank-
ing,so they all have "bypass"methods to ensure sufficient spark energy.
MSD and other discharge type systems don't use the saturation method,instead
they they "bombard" the coil primary w/100's of volts multiple times w/capacitor
discharges,thus no heavy current draw except thru the ign unit itself,which is
designed for this purpose,thus no ballast at the coil needed.:coffee2:
Click to expand...

Exactly!

Right out of the manual!
 

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67Dart273 said:
Sorry, but depending on what ignition he's running, this STILL is not correct. If you run a factory - like Mopar electronic, a ballast is required.
Click to expand...

Correct we don't know, but even with a mopar electronic ignition and say a msd blaster coil wouldn't the ballast have no purpose ? I always thought the ballast protected the older low voltage coils and points.
 
65-440 said:
Correct we don't know, but even with a mopar electronic ignition and say a msd blaster coil wouldn't the ballast have no purpose ? I always thought the ballast protected the older low voltage coils and points.
Click to expand...

This gets sticky. "Ma" never intended for you/ us to play around with different coils. Aftermarket HP coils have different current requirements, and this "changes things"

At least one of the Accel and the old Mallory rectangular coil required a SECOND resistor IN SERIES with (in addition to) the factory resistor.

In the early 70's, I walked up to a kid with a 55 chev just in time to see one of the (then new) Mallory coils explode, oil all over the firewall and engine. he had not read the destructions, and had installed it by replacing the factory resistor (55 had a block resistor, not a wire) with the Mallory.

He'd left the key on for some reason, and the points obviously had been closed.
 
65-440 said:
Correct we don't know, but even with a mopar electronic ignition and say a msd blaster coil wouldn't the ballast have no purpose ? I always thought the ballast protected the older low voltage coils and points.
Click to expand...

100% wrong!!Don't confuse using an MSD coil with using their ign. system.The
blaster series coils actually have a LOWER primary winding resistance, and a much
HIGHER current demand,generating even more heat than the OEM unit.The factory
Electronic Ign. still needs a ballast,and the transistor kept cool as poss.,it is not a
computerized ign. or a "discharge" type ign. as I explained above.
 
so enlighten me please .... why can I delete the ballast and run battery voltage to the coil of a pertronixs ignitor 2 w/ matching coil, but not a mopar performance ignition with non-factory coil ? ... I'm confused as to why I would need the ballast if I no longer have points or the factory style low voltage coil ......Thanks (oh by the way, I know running an msd coil is not an msd ignition system )
 
Simple. Read my last post again. It's the way Ma designed it. That transistor will only switch so much current. You can easily exceed that current by playing with low resistance coils, ballast, or no ballast. I have no idea what that value might be. Not all transistors fail "the same." We've got guys claiming they ran a Mopar ECU with no ballast, and others saying they failed in fairly short order.

You are not just dealing with the coil, but the limits of the ECU itself.

Also, not all Mopar "look alike" ECUs are made the same. Just to pick "from the blue sky" it might be that some of the older high quality Blue Streak units are better than Mopar, or vice versa.
 
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