Anyone ever wired up an ignition coil resistor before?

I got told i needed one and after asking the local auto shop guy how to do it, the car doesnt even start. I have wired one side to the + terminal and the other to the -'ve of the coil. Is this wrong?

The wiring diagram for a 72 fasty doesn't show a resistor. Why do you think you need one?

http://www.thesamba.com/vw/archives/info/wiringt3.php 

well i bought a new coil for it, a GT40. Apparently they put out 11v when the engine's ignigiton system is only designed for 9v or something along those lines. It was recommended i put one in by my mech.

Well coils put out many thousands of volts so I'm not sure what they meant. Does anyone know more about this?

i got little bits of advice from here and there when i put my electronic points kit in. i had a gt40 and some people sead i needed a resistor and some not.

in the end not wanting to stuff anything up, i checked what was on a freinds bug and copied it. su12 coil and accufire setup. no resistor.

now i have the existing gt40 and points and condenser in the spares kit.

i dont think this has helped you though...:jesus

72fasty

If you have a resister type coil - check on bottom of coil, it will have words "Use with resister"
then you will need a resister to go with it - usually a white porcelain block about half the size of a matchbox.

The positive (ignition power) goes to one side of the resister with the other side of the resister to the positive on the coil. This supplies the 11volts or sometimes 9volts to the coil.
You must remember to take the power for the choke and idle solenoid from the input side of the resister ie 12volts, not from the coil (which will only be 11or 9volts).

If you want to get fancy (like in modern cars) then you can run a wire (which must include a diode) from the starting circuit to the positive side of the coil. This will give 12volts when cranking to the 9/11volt coil. Gives it that extra boost to compensate for the "drain" the starter motor is taking from the battery.
Works a treat - and yes I have this setup!

Thanks old dubber. You raise an interesting point about the choke/idle which i hadnt though off. Basically from the research ive done, the resistor is used to save burning out the points and thus replacing them frequently from using the new slightly overpowered(?) coils. (forgive my electronic ignorance)

I have it installed and all is working fine now, although ill have to change that choke/idle wire to the input side of the resistor!

I guess its a $10 investment to be safe, rather than sorry every few hundred miles....

Old dubber is quite correct about the ballast resistor and where it goes.

Check out your starter motor as many starters have an auxiliary terminal just for the purpose of supplying a switched 12 feed to the coil side of ballast resistors.

If you simply run a wire from your pull-in lead on the starter motor, the starter will continue to stay engaged while ever the ignition switch is on! Hence the diode in the wire to prevent the coil power from backfeeding the starter solenoid.

You can also employ a simple relay, pulled in by the starter wire for the purpose of supplying 12V direct to the coil for reliable starting without the drama of holding the starter on with ignition.

This setup is the primary reason for using a ballasted system.

L8tr
E

relays are are better option as there is no foward conduction loss thru the diode. ,reverse polarity applied to a diode will result in infinate impedance(not really but near enough for our purpose) but foward polarity results in .6v across the junction of the wafers inside the device.the idea of putting a ballast coil in the first place is to get maximum voltage to the coil for starting purposes

I think this question is on topic. What's the difference between the GT40 and the GT40R?

Does it mean one of them needs a resistor or has one built in or something? I've never understood.

Dunno, but here is an interesting article about Bosch Blue Coils. It describes how to tell if a resistor is built in by measuring the resistance of the primary coil:
http://www.ratwell.com/technical/BlueCoil.html 

gt40 is a 12 volt coil and the r signifies that it must be used with a ballast resistor

Thanks for that topless. You have solved a long standing mystery for me.