Honda Repair: Third brake light and defroster, honda civic dx, 1994 honda civic dx

Question
Greetings matthew. Hopefully you can answer this, as so i can avoid going insane.
I have a 1994 Honda civic DX hatchback Automatic. I noticed that the rear defroster and third brake light went out. I replaced the bulb and nothing, also the deffoger switch light comes on, but doesnt do much.
Could it be the relay? even though i hear it clicking when i push the rear defogger switch. Thanks and hopefully this isnt the first time this problem has occured wiht this generation honda.
Regards
Samson, P
Toronto, Ontario Canada.

Answer
It sounds like you have a ground issue. The high mount brake light & the rear window defogger both share the same ground point. So, if the circuit is ok, you hear a relay click when you push it, that is a sign that the circuit has power, but the power has no path to ground. I looked at a schematic on your vehicle & ground 553 controls both components. This ground is located on the center of the rear shelf in the trunk area.