How to Replace 3 Lamp Instant Start Ballasts

Replacing a ballast of the same type (3 lamp with 3 lamp, instant start with same) is fairly simple. The wiring connections and colors match up.

3 Lamp Instant Start Ballast Replacement Diagram

Replace 3 Lamp Parallel Ballast with 4 Lamp Parallel Ballast Wiring Diagram

3 Lamp Instant Start Ballast Replaced with 4 Lamp Instant Start Diagram

Replace 3 Lamp Instant Start Ballast with 4 Lamp Instant Start

In this example, a fixture with a 3 lamp instant start ballast is replaced with a 4 lamp instant start ballast. The colors of the old and new ballasts do not match, making this a little confusing. The two yellow wires on a 4 lamp instant start ballast are connected together inside the ballast.

Cut and cap one yellow and one red or blue wire with a wire nut.
Connect each of the blue ballast wires to each of the two blue lampholder wires.
Connect the red ballast wire to the third blue lampholder wire.
Connect the yellow ballast wire to the red lampholder wire.

3 Lamp Instant Start Ballast Diagram

Factory wiring