Step 1: Safety
Step 2: Parts Used
I used a flush mount utility LED light from Home Depot, along with three 6-32x5/8" screws and nuts, and three brass 8-32x3/8" screws. The exact screws required by your fan/light combination may be different, please look your setup over before starting.
The switch is a single pole pull chain switch, with a 3/8" hole drilled through the lip of the light housing to fit it.
I also used a 5/32" drill bit to drill the holes in the closure cap of the existing fan, and a 3/8" bit for the switch hole and wiring hole.
Step 3: Find Power and Start Modifying
The mods to the light itself are fairly straightforward: The three screws that hold the LED panel to the light housing are replaced with the longer 6-32 screws one at a time. I pulled one screw, centered the light on the fan closure cap, and marked through the hole where to drill the cap. I then drilled the cap, installed the longer screw in the light, and used that to hold the cap in position while marking the next hole, and the same for the third. Once all three holes are drilled and the screws installed set the cap aside. Most of these caps can only be installed one way, so think about where you want the pull chain to be, then drill the hole and mount it. One black lead from the switch will be wired to the fan wiring, the other gets connected to the black lead coming out of the light using one of the wire nuts supplied with the light fixture. The white lead from the light gets connected to the fan wiring.
Tuck the excess wires into the rim of the light fixture and fix in place with a dab of hot glue.
Step 4: Fan Modifications
Once the cap is attached to the light and the wiring is passed through the hole, it's ready to install.
Step 5: Installation and Test
With the wiring complete, carefully put the light into position and install the cap mounting screws.
Turn the power back on and give the light a test. If it turns on and off, you're done. Now you can sit back and enjoy the benefits of upgraded lighting.