Two Ballast Resistors

[Sixt8Chrgr]

I had a stock ignition wiring harness and upgraded to a MP electronic setup with a chrome box. The directions for the installation suggest to leave your old ballast resistor in the circuit. I had to splice in a 12v supply for the new resistor, so now I have two ballast resistors per the directions. This seems odd to me. Can someone explain to me why this is correct.

Thanks,

[tomfed]

Don't quote me but i think if you replace with the 4 prong resistor that's all you need.You went eletronic IGN correct? Rewire it to the 4 prong and your done.that will get rid of 2 resistors.

[Nacho-RT74]

simply wrong... is one or the other, but not both

you can use either one, on same existing plugs and locations. The only diff it is the ohms value. Use the lower to match with ECU

note... MP kit provides 2 prongs not 4 prongs ballast resistor

[Sixt8Chrgr]

simply wrong... is one or the other, but not both

you can use either one, on same existing plugs and locations. The only diff it is the ohms value. Use the lower to match with ECU

note... MP kit provides 2 prongs not 4 prongs ballast resistor

Nacho...the directions say to use both...read them myself. I am not too fired up to being using both...looks stupid but what choice do I have? Don't want to burn the car up or deprive a circuit of the correct voltage.

[A383Wing]

if you use both, you are depriving the circuit of the correct voltage....

[Topher]

What he said.

[Sixt8Chrgr]

The original ballast resistor is still hooked up as original. The "new" ballast resistor is hooked up with a 12 volt jumper from the wiring harness and the other side of the resistor is hooked up to the lead coming from the new wiring harness that goes from the distributor to the chrome box. How is this depriving the car of the correct voltage?

Thanks

[Nacho-RT74]

I don't care what instructions says... whatever you read using both ballast is WRONG. Ballast resistor is just one to coil no matter if points or electronic, nothing more nothing less. Is not directly in ECU relation ( on 4 pins Modules ). The dual ballast resistor, so the 4 prongs, is the only one what relates directly with ECU but just to 5 pins ECUs

you simply keep original wiring, and splice one wire from blue wire ( ign side RUN circuit, full 12 volts. ) of ballast, no matter wich ballast to ECU... thats all what you need... rest of ECU wiring on kit runs by itself  without any splice any kind, just tape it together to the existing wiring ( green traded red wire not used on 4 pins single Ballast, simply hide it down the tape  )


they also states on instruction sheet about the yellow wire coming from starter solenoid to resistor what is juts valid for 75 ... or it is 77s don't remember, and lates, but it doesn't talks is TO VERY LATES MODELS, so lot of ppl has been confused about that setup.


( BTW, there is something wrong on the way you wired the system, didn't catch but sounds weird )

[Sixt8Chrgr]

I don't care what instructions says... whatever you read using both ballast is WRONG. Ballast resistor is just one to coil no matter if points or electronic, nothing more nothing less. Is not directly in ECU relation ( on 4 pins Modules ). The dual ballast resistor, so the 4 prongs, is the only one what relates directly with ECU but just to 5 pins ECUs

you simply keep original wiring, and splice one wire from blue wire ( ign side RUN circuit, full 12 volts. ) of ballast, no matter wich ballast to ECU... thats all what you need... rest of ECU wiring on kit runs by itself  without any splice any kind, just tape it together to the existing wiring ( green traded red wire not used on 4 pins single Ballast, simply hide it down the tape  )


they also states on instruction sheet about the yellow wire coming from starter solenoid to resistor what is juts valid for 75 ... or it is 77s don't remember, and lates, but it doesn't talks is TO VERY LATES MODELS, so lot of ppl has been confused about that setup.


( BTW, there is something wrong on the way you wired the system, didn't catch but sounds weird )
[/quoteGot it thanks.

[John_Kunkel]

Not knowing exactly which wire is getting the second ballast, it's possible that the second ballast isn't reducing the voltage to the coil. If the second ballast is in the ECU "activation" circuit it won't affect the coil voltage, that wire merely turns the ECU on/off.

[Nacho-RT74]

here is the basics of the ECU wiring, to make it work. ( one image better than thousands of words )

Note:
the light blue traced yellow wire of ECU harness section can be spliced to ballast RUN circuit OR IGN SIDE of regulator what is also sourced from RUN circuit

( an advice upgrade regulator for an electronic unit )

[Sixt8Chrgr]

I will confirm the wiring and come back for your input.

Thanks guys, I appreciate it.

[TylerCharger69]

When i converted  it required a different resistor  so the instructions said......but not to use two

[Sixt8Chrgr]

Nacho,

You were right...only needed one resistor. Thanks for the help.

Lawrence

[70daytonaclone]

Thanks Nacho for the drawing. as this is what I need for my car. I was looking at a 72 motors manual and it was different with the wire layout. QUESTION... is there a right or wrong  way to use a ballast? Is there a top or bottom? Mine has 2 holes in it. one on the edge and one on the inside of the white stone. Does it matter which way I mount it? thanks  70DC

[John_Kunkel]

Going back to the original post, I stumbled across an old set of instructiions for the mechanical advance electronic conversion kit and it does show the use of a secondary single ballast along with the dual ballast.

All three ballast resistances are .5 ohms.

[Nacho-RT74]

QUESTION... is there a right or wrong  way to use a ballast? Is there a top or bottom? Mine has 2 holes in it. one on the edge and one on the inside of the white stone. Does it matter which way I mount it? thanks  70DC

yes there is but just for one reason, you have two resistors in double ballast. One is secondary other one is primary.

Doesn't matter which side you plug them but you can't plug them ( or shouldn't plug ) turned around.

double ballast plugs have a key stud to fit on those holes to be sure you plug them correctly

[Nacho-RT74]

Going back to the original post, I stumbled across an old set of instructiions for the mechanical advance electronic conversion kit and it does show the use of a secondary single ballast along with the dual ballast.

All three ballast resistances are .5 ohms.

I just can see one reason for that... by ohms law, parallel circuits make smaller resistances. Maybe 1/4 ohms ballast weren't available on those days, so they optioned to ad a parallel single ballast with stock value to get lowered the sumatory of the stock dual primary and stock single