DETERMINE IF LIGHT FIXTURE IS BAD - If your light continually trips the GFI circuit, there's a good chance that it has developed a short in the light fixture or wiring. At this point you will have to replace the whole light fixture and wiring. If you have two lights tied together than you will have to wire each light independently to test which light is tripping the GFI.
TURN OFF POWER - Before working on your light fixture, be sure to turn OFF power to your lights at the circuit breaker.
DISCONNECT LIGHT WIRES - Locate the power junction box for your lights. It will normally be next to the house close to the pool control box. Open up the junction box and disconnect the wires to your light You may have several light cables coming into this box. Generally they are labeled on the PVC pipes. If not, you may have to disconnect each independently and turn the power back on and off to see which cable powers each light. Mark the pipes for the future.
ATTACH CORD TO POWER CABLE - Once you have determine which cable you want to pull out, attach a cord or special fish tape to the wire. One way to do this is to bend back the white and black wires to form a loop. Leave the green ground wire out straight. Then attach the cord though the loop. The green ground wire will parallel the cord as shown.
TAPE CONNECTION - Tape the wire connection on both side of the joint so that no wire ends are left exposed. A smooth connection will move around any bends in the pipe more easily.
UNSCREW LIGHT FIXTURE - Remove the light fixture off the pool wall. It is generally secure by one screw at the top of the light fixture.
PULL FIXTURE OUT OF NICHE - Pull the pool light fixture out of the niche. You should have enough excess cable to be able to lay the light fixture on the pool deck. Note how the excess cable is stored in the niche so you can replace it the same way when you install the new pool light fixture.
PULL LIGHT CABLE OUT OF WALL - Pull the light cord out of the pool wall. There is a conduit between the pool and the J-Box at the house. When you pull out the light cable at the pool, you will be pulling the cable out of the conduit and pulling through the cord that you attached to the other end
FEED CORD AT THE J-BOX END - As you are pulling cable on the light fixture end, have someone else feed the other end of the wire and the attached cord down into the pipe.
PULL_OUT_CABLE-CORD_CONNECTION - After you have pulled out all the old cable, you will expose the connection of the cord and cable created at the junction box.
TIE CORD TO NEW POWER LINE AT POOL - Once you have pulled the old light cable out of the conduit, take off the cord that was pulled though with the old cable and secure it to the free end of the new light cable. - like in Steps 4 & 5.
PULL NEW CABLE AT J-BOX - pull the new light cable back into the conduit by pulling on the cord at the terminal box end of the conduit. Have someone feed the cable into the conduit at the back of the pool niche so that it doesn't bind as you are pulling on the other end.
LEAVE 4' SERVICE LOOP AT POOL NICHE - Pull the cable through the conduit until there is 4' of cable left at the pool side. This extra 4' will allow you to place the light fixture on the pool deck when you have to service the light in the future.
PLACE NEW FIXTURE INTO NICHE - Position the new light fixture in the niche by first recoiling and storing the excess cable as observed in Step 7. Then push the light fixture back into the niche.
REPLACE PILOT SCREW - Replaced the single screw to secure the pool light fixture to the niche
REMOVE EXCESS CORD AT J-BOX - Go back to the J-Box end of the cable and cut off the extra length of cable, leaving about 7 extra inches.
ATTACH WIRES TO J-BOX -Use wire strippers to strip 6" of the outer cable casing to expose interior wires. Strip about 1" of wire coating off each wire and attach the cable wires to appropriate wires in J-box.
REPLACE J-BOX COVER - Replace the J-Box cover and secure it with the screws removed in Step 3.
TURN POWER ON - Turn the power to the lights back on at the breaker box.
CHECK LIGHT - Check the new light at the pool to see that it is operating properly.