electrical and ignition Ballast resistor - replace with external?

[theNomad]

So I started the car up for the first time since February or so. Happy to be at this point.

Of course I made a mistake with wiring it up and melted up the Ballast resistor wire. Slapped myself and put it on the right connection. 
It works but obviously needs replacing. 

Anyone just wire up a .9 ohm ballast resistor from the parts store instead of trying to find the "speaker wire"? I can't imagine any downside but I've got limited experience.

 

I'll be installing a Hotspark electronic ignition shortly as well and I have the original Black coil working fine.

After reading the install it seems this ballast resistor may still be needed? 

[JohnS]

What year is your car?  It's my understanding that the '74 and later non-tii 2002s used a 0.9 ohm resistor wire.  You should remove that section of the burnt resistor wire and replace with the correct gauge regular wire.  If you can read the numbers stamped into the bottom of the black coil I can probably figure out what resistor it takes based on the Bosch part number.  I own black coils that take a 0.9 ohm resistor and I own black coils that take 1.8 ohm.  The part number is the best way to confirm which resistor is correct for your coil.  Some of the coils have a sticker on them that tells you which resistor it needs.  Or, get a 1.8 resistor and a "red" coil.  or a blue coil and no resistor.  If you hook up a resistor, place the red power for your Hot spark before the resistor so that it gets the full 12 volts when the engine is running (not the stepped down voltage after the resistor). 

 

Take a look at the Article called 'Ignition Coil Myths Busted' in the Electrical articles section of this site. 

 

Hope this helps.  

John

Edited April 28, 2016 by JohnS

[theNomad]

thanks, I found a used one so hopefully that does the trick. I also just saw the resistor as you picture it in the haynes manual so I'd do that in the future if needed.

[Stevenc22]

You can use ballast resistor instead of the later model resistance wire. Just get the right size ballast and remove the old resistance wire replacing it with regular wire.

 

If you keep the black coil, you will always need a 0.9 ohm resistor since the electrical circuit needs 3 ohms total resistance. If you ever change coils and get a blue coil, then you will not need a resistor since the blue coils have 3 ohms of resistance built into them.

[theNomad]

Yeah, I have a '74 and have a wire coming. In the future I can always change it but on a slim budget I'm only touching what's necessary now. Thanks all!

[Phantom]

After reading many different threads on here about this issue I'm having some issue with my new setup.

 

I purchased a red coil (silver with red label) and an bosch external resistor (1.8ohm) similar to the one in Johns post above. But Before I bought the bosch resistor I tried a cheaper one that was at a local shop, but it fried as soon as I turned the car on. (Same resistance, smoke was coming out of it and looked toast on the inside) I don't want the same thing to happen to the Bosch one I had to order. So before I install it I was wandering if anyone has had similar experiences or advice.

 

'72

Edited May 6, 2016 by Phantom

[Stevenc22]

NM

Edited May 6, 2016 by Stevenc22

[JohnS]

Phantom,

  Looks like you have a '72.  What was the old coil setup on your car?  Was it running before you changed things?  

John 

Edited May 6, 2016 by JohnS

[Phantom]

Looks like it was the stock setup. I'm not entirely sure. The old stuff looked pretty worn and needed to be replaced.

I was driving it around the engine died and I had no idea what I was. I narrowed it down to the ignition coil or resistor because I get no spark out of the coil.

[theNomad]

swap the resistor and see.

[theNomad]

On 4/28/2016 at 6:25 PM, JohnS said:

  If you hook up a resistor, place the red power for your Hot spark before the resistor so that it gets the full 12 volts when the engine is running (not the stepped down voltage after the resistor). 

 

So if I have the stock resistor wire is the hot spark + ok to connect to the + 15 terminal? It would not be 12v because it would already be stepped down. If it needs direct power I'd need to run a whole new wire. Do you have a hotspark connected on yours in that photo? Wouldn't that actually be stepped down power as you show a resistor in line?

[JohnS]

Hi Nomad,

  Mine is using a Pertronix (same idea as a HotSpark) and you can see in the photo that the Red wire with the Red push on connector is connected before the resistor, so it gets the full 12 volts.  The stepped down voltage is what comes out of the other side of the resistor and connects to the coil (Red and Green wire).  When using a resistor wire, you do need to either run an additional wire from the fuse box, or splice in an additional wire right where the resistance wire begins, not where it ends at the coil.  I had to do that on my '74 2002tii that has a resistance wire.  Good luck,

John

 

[theNomad]

Isn't the 12v coming from the wiring harness green wire into the coil at the + terminal then going to the resistor, then after the resistor it is 9v going to the red wire? I'm not good with electronics so maybe I have the flow wrong? I guess I do.

 

Your wiring looks different. Is the hot 12v coming from the right angle spade? I guess that's where I'm confused. I have a large connector as seen on the coil coming from the harness.

Edited May 6, 2016 by theNomad

[JohnS]

This should explain it for you.

 

#1 (solid green wire with right angle spade) is hot when the engine is running. (stepped down voltage after the resistor).

#2 is hot when the engine is being started (full voltage from battery for extra boost when starting)

#3 positive wire to Pertronix.

#4 negative wire to Pertronix.

#5 (solid black wire) to negative terminal on coil.

 

Green arrow is the current flow when the engine is running.

Red arrow is the current flow when the engine is being started.

 

 

 

 

Edited May 6, 2016 by JohnS

[JohnS]

12 hours ago, Phantom said:

Looks like it was the stock setup. I'm not entirely sure. The old stuff looked pretty worn and needed to be replaced.

I was driving it around the engine died and I had no idea what I was. I narrowed it down to the ignition coil or resistor because I get no spark out of the coil.

 

The spade connector with two green & red wires going into it should be on the + side of the coil.  See my picture above with the numbers for an explanation.  Hope this helps,

John

Edited May 6, 2016 by JohnS