In my neighborhood there are walkways with what appear to be lights however none of them would come on at night. So what is the first thing to test when a light doesn't work? The bulb. After popping open the cover and seeing what work needed to be done, it turns out that it is slightly more involved then just replacing the bulb. However with a few simple tools the job takes less than 5 min per bulb and the results are worth it.
Step 1: Tools Needed
Philips screwdriver - Removing the cover
Wire brush - Cleaning off the lens / housing surface
Light bulb - WLED-WWLX LED bulb (warm white) - Note: The old bulb was a 24v -194 incandescent bulb that probably lasted a couple of years with the lights always on. The new LED bulb should last for several years to come and use far less power.
Dielectric grease - Seals out water from the connector to prevent the spread of the nasty green stuff (rust) that electronics hate
Clear RTV - Help keep dirt and water out of the light housing
Electric Parts Cleaner - For cleaning out the connectors - Note: The outdoor lighting system that I was working on was always live, so any cleaners used must be rated for use on live (powered up) electrical systems
Compressed air can (the stuff used to clean computers) - Although not necessary helps to quickly dry out the connector after cleaning
Step 2: Inspect the Damage
Step 3: Cleaning
DO NOT use any metal tools to clean the connector if you can not turn off the power.
Using the wire brush clean off the housing and the cover so the RTV can make a good seal. This doesn't need to be perfect just get the loose dirt / crap off of both sides.
Spray down the connector some more and blow dry it clean with the compressed air can.
Step 4: Assembly
Put in the new light bulb. It may take some wiggling and removing and reinstalling several times to get the rust off the connector and get good contact. Just make sure to wiggle the bulb once it's in to verify a good connection. Remember it takes longer to redo a project than to do it right the first time.
Make a small bead of RTV going around the entire housing lip. It doesn't need to be pretty or perfect.
Install the cover
Step 5: DONE!
Don't be intimidated by this project, you are quite literally changing a light bulb, nothing more.
If either of the screws holding the cover on are stripped, Google stripped screw removal there are many different tools and techniques to help.
Don't be the person to strip the screws, they don't need to be supper tight.
Just an hour spent doing several lights makes a big difference in the feel of ones yard and is well worth the effort.
Auto part stores have almost all of the chemicals needed (just not the compressed air can)
The bulbs can be found at supperbrightleds.com Part #: WLED-WWLX However any 24V AC miniature wedge based bulb should work. These were just the cheapest LEDs I could find that would work.