Pool & Spa Light Problems

            Light "Problems" center around lights that "don't work". (Duh)
        There are many different types of lights from fiber optics (Whose light source and electronics are above ground), to LED lights, to the standard bulb in a sealed metal housing, has a regular bulb (Albeit up to a 400 watt one) with a long cord. Since there is one thing that all of these have in common. Electricity.
                I detail a recent light electrical diagnostic HERE. Take a look. Basically it all boils down to figuring out where the electricity "stops". Here are the areas where electrical problems can be.
1.) At the Main Breakers
2.) In the Wiring  between the Main Breakers and the Sub Panel ( And yes, in about a dozen instances, the customer didn't even know there was a sub panel. They can be small. ) 
3.) At the Sub-Panel Breakers
4.) Between the Sub-Panel Breakers and the Equipment area.
5.) Between where the wiring comes out of the Ground and the Timer / Control System
6.) In the Timer / Control System
7.) In the wiring between the Timer / Control System and the switch.
8.) In the Switch (Yes, Switches Go bad)
9.) In the Wiring between the Switch and the GFCI
10.) In the GFCI (Note: The GFCI can be in a number of places altering the order somewhat.)
11.) In the wiring between the GFCI and the Light Connection Box
12.) In the Light Connection Box
13.) In the Wire between the Connection Box and the Sealed Light in the wall of the pool
14.) In the light housing itself
15.) In the bulb socket itself
16.) The bulb
        If you go through the diagnostic process in the electrical diagnostic area, (See Link Above) you will see that I try to test the bulb from above ground, without pulling the housing out of the wall of the pool, and check the current to the cord that attaches to the light at the same time.
        Keep in mind that, as in the case mentioned in the link, there may be more than one problem. Test at each position to make sure there is current, and wherever it isn't getting to, the problem is in that device or set of wires.