How to Connect a Ballast Resistor

What You'll Need
Ballast Resistor
Wire Cutter

In the years when engines were a lot easier to work with, a ballast resistor was used in order to prolong the life of the coil. In a points type ignition, the ballast resistor would help to keep the spark down, and the coil from being burned up too quickly. Of course, this meant that there was going to be a little less power getting to the coil. Connecting a ballast resistor is a fairly straightforward project, but you will want to pay attention to the wiring.

Step 1: Determine if Ballast Resistor Is Needed

In many of today's vehicles, the ballast resistor is not needed. However, in older vehicles where the points ignition is still present, you need to use this type of spark resistor to ensure that the coil does not burn up too quickly. Determine whether the coil is a 9 volt or a 12 volt coil. Since the resistor lowers the overall current 3 volts, you want to use a coil that will not be bogged down by the lower current.

Step 2: Locate Ballast Resistor along Firewall

The best location for the ballast resistor to be connected is close to the coil along the firewall. This will not only give you a better attachment point, but also keep you from having to run wires all over the engine compartment. Choose a location near the coil and mark your placement.

Step 3: Drill Holes for Securing Resistor

The ballast resistor will be attached to the firewall with small clamps that are screwed in place. To do this, you need to drill small holes. Hold the resistor up to the firewall and mark the holes where the clamps will go. Set a drill in the place, and carefully drill the pilot holes for the screws.

Step 4: Install Ballast Resistor

Set the ballast resistor up to the firewall and screw the clamps in place.

Step 5: Connect Wires to Positive

Strip the end of the positive wire from the ignition, and connect it to the positive end of the resistor. From there, a wire goes to the positive on the coil. Make sure to attach securely to the connecting terminal, by wrapping the wire around the post and tightening with a screwdriver.

Step 6: Connect Negative to Condenser

The condenser is a small canister that handles some of the load of the current. It is located with the ballast resistor on the firewall. Install it the same way as the resistor. Once it is located on the firewall, connect the negative wire from the ignition to the terminals. Run another wire from the condenser to the negative on the coil. Attach the same way that you did with the resistor.

Step 7: Start Engine

With the installation of the ballast resistor completed, start the engine and let it run. You should notice that the engine runs smoother, and without any type of hesitation. The only way to really know whether or not the ballast resistor is doing its job, is to take it for a drive and see the smoothness of the ride.