How do I bypass the ballast resistor?

[Tom W]

I've just bought an electronic ignition module and suitable coil from http://www.aseriesspares.co.uk/

The kit is designed to run without a ballast resistor. The wiring diagram for my car ('76 2200tc) shows the ballast resistor is fitted inline between the coil +ve and a lucar connector joining a bunch of white wires that operate a lot of warning lights on the dash etc. Whereabouts is this actually located on the car? I'm thinking it will be behind the dash module somewhere. I will need to bypass this to get the electronic ignition to run correctly.

Thanks,

Tom

 

[Willy Eckerslyke]

When I did mine, I just took an ignition controlled live feed off another component under the bonnet. The heater fan, I think. Anyway it works and was close enough not to need any complex routing of the new wire.

 

[arthuy]

I posted photos a while back. If you search back you should find them.

Mine runs from behind the dash next to the shunt to the engine bay near the bumper mount on the drivers side.

If you remove/bypass the ballast wire will you be swapping the coil aswell?

When I have fitted these kits I run a fresh 12v supply for the unit but you have a few option of points to take the 12v from.

Colin

 

[Tom W]

I've bought a bundle of the electronic module, new red rotor arm and matched coil, so I understand I should be running without the ballast resistor. I plan to bypass the ballast resistor to keep the wiring as standard as possible. I just need to find where it's hidden on the car.

 

[Fraserp6]

Hi Tom,

My understanding is that, the Ballast Resistor isn't an actual resister in the sense that there is an item you simple bypass.

Its actually a length of resisitve wire thats run (if I remember rightly) from the back of your Rev counter to the coil.

Best place to start is probably the wiring diagramme in the Haynes/Workshop manual or have a look behind the dash, from memory the wire is white and yellow.

Fraser

 

[Tom W]

I've done a bit of investigation behind the dash and I think I've identified the ballast resistor wire. According to my manual it is white and pink and connects to a white wire one end, and white an yellow at the other. I've found a white wire behind the dash connected to a white and pink wire, and a white and pink wire connected to white and yellow on the driver's side inner wing. Assuming I've identified the correct wire, presumably I cut the existing connections and run a new (low resistance) wire along the same path as the old one and reconnect it to the loom both ends. What spec should the new wire be? The white and pink wire seems to be the same gauge as all the rest of the loom.

I've attached a couple of pics of the wire I've found in the hope someone can identify if I've found the correct wire before I start to cut anything.

 

[arthuy]

That looks like the job.

If you follow the white back from behind the dashboard you get to the fuse box.

I would cut the existing one off at the connector and run a complete length of wire to the coil instead of just patching in the existing wire.

Colin

 

[Tom W]

I think I've worked it out now. What was throwing me was the coil also receives an unballasted 12v supply from the starter solenoid, presumably to give stronger spark when starting. I'm going to perform some checks with the multimeter before I cut anything, but I'm planning on disconnecting the existing ballast wire, and running a standard wire in it's place, and securing it to the rest of the loom. This will be easier than dismantling the loom to trace the wires back to their terminals, and it will allow me to reconnect the ballast wire in the future should I need to return to points for any reason. Any idea what gauge cable I should be using? Presumably too thick is better than too thin.

Thanks,

Tom

 

[DaveHerns]

What was throwing me was the coil also receives an unballasted 12v supply from the starter solenoid, presumably to give stronger spark when starting.

That is indeed the purpose of the ballast resistor - to keep the spark power up when battery voltage is depressed by cranking the engine over