T12 Ballasts

T12 Ballasts have been around for decades and are used for industrial and commercial use given their reliability and powerful control of lighting – however, they are beginning to become swamped out for more efficient T8 Ballasts when they eventually do start failing (which often can be after decades!)

If you notice your Advance T12 ballast light flickering, or if it just stop working all together, then you will likely have to fix or change the ballast.

Advance T12 Ballasts are not easy to come by – you can find some on Amazon.com or eBay – but some may be used, or surplus lots. If you cannot find a replacement, we recommend swapping your T12 Ballast out with a T8 Ballast. Below are instructions on how to do it!


Step 1: Determine Current Ballast Specifications

Before buying a new ballast, you need to understand which one you have to ensure you buy a replacement that actually works and is compatible. This will be much easier if a label is on the old ballast. You will need to locate the following:

  • Identification code (example: F4T12)
    • The “F” denotes fluorescent, with the number 4 in this case being the power in watts or length in inches if you have a long lam
    • The T” denotes “tublar shape” and allows you to confirm if you have a T12 fixture

Step 2: Buy the Replacement Ballast

After confirming you have a T12 Ballast, you can now shop for a replacement T8 ballast that you can purchase from a distributor. You will want to:

  1. Check the Advance cross-reference guide For best prices, we recommend Amazon.com
  2. Purchase the replacement ballast via a distributor, we recommend Amazon.com for best prices and fast shipping
  3. Can’t find a T8 Ballast? You can find T12 ballasts still around – try eBay!

Step 3: Disconnect the Power for Safety

Prior to removing the T12 Ballast, it is strongly advised to disconnect the power to the fixture. You can accomplish this by turning the switch to the off position thereby cutting power by way of the circuit breaker. If you cannot, you should also use insulated screwdrivers to remove any screws for added protection. If there fixture is located in a dark area remember to bring a flashlight or change it during the day for natural light.

Step 4: Diffuser Shield Removal

The diffuser shield more evenly distributes light and will need to be removed along with any tubes located inside. We recommend using gloves with some insulation in case there is any electric conductivity in any metal housing.

Step 5: Disconnect Wires

To disconnect the T12 wires, please follow these steps:

  • Find the pairs of black and white wires routed into the fixture from the ceiling.
  • Remove the wire nuts and disconnect the wires.
  • Replace the wire nuts on the ends of the pair that is routed down from the ceiling to avoid risk of shock in case the power somehow is turned back on
  • Remove all wires connecting the ballasts to the quick connect ports located at the end of the fixture and unscrew the holding nut from the ballast to allow it to free off
  • If your ballast does not contain wire nuts, the alternate method is to sever the the wires in place of disconnecting them – it is a good rule of thumb to cut them about 12 inches from the middle of the ballast

Step 6: Replace the Old With the New

Prior to connecting the T8 Ballast that will replace the T12 ballast, you will need to add a jumper. This can be accomplished by connecting the outside ports on the tombstones on one end of the ballast.

For a two-bulb fixture, only one jumper should be required although four-bulb fixtures will require two – one for connecting the external ports on one pair of continuous tombstones and another for the second set.

Mount the new ballast in place and begin connecting the wires – for the 4-bulb fixture, one side will join two red wires and two blue wires to the four tombstones – and will join in this organization – 2 red along each other and the two blue on the other. On the other end, just connect two yellow wires each to an available open slot for each socket connected by a jumper.

Once done, all that remains to do is to connect the black & white wires to the ballast with those dropping from the ceiling with wire nuts.

Step 7: Wrap-Up/Test

Install the new T8 light tubes and reinstall the light diffuser into the ballast. Turn on the circuit breaker and turn on the fixture to verify you installed everything correctly!

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