1990 lamp failure sensor (brake lights out)

I had my yellow lamp failure sensor box go out, but had managed to keep it up and running for a couple of months with a soldering. However, it's
failed again, and the replacement from the junk yard wasted no time in failing as well. I don't know anything about electronics, but having checked and replaced all the bulbs to make sure the proper ones are inserted and in good shape, I assume the lamp failure sensor is burning up due to a bad ground somewhere. I don't see any signs of distressed wiring, even around the trunk hinge.
Is there a tool I might buy and check things out myself with a little instruction, or is my next stop an auto electrician (who I fear will tell me I need to replace the wiring harness)?
By the way, my power antennae went bad (would crank down but not up). The mechanic manually got it into the up position. Then, to keep it from maneuvering down again when I shut off the radio, he disconnected the wiring to it by unpluging the connector at the top of the blue box (that sits just below the yellow lamp failure sensor box). Would disconnecting this have any affect on the current to the lamp failure box that might cause it to fail? I also notice there is a larger plug at the bottom of the blue box. Would it perhaps be better to unplug that one instead? I'm a blind squirrel reaching for straws here, to mix a metaphor.
One other note... I had the engine replaced not long before this problem started. Is there some common oversight the mechanic might have made in relation to the electronics when installing the new engine... one which ulitmately might have led to this problem? If so, perhaps its something I can check on.
Lastly, and totally unrelated... out of curiousity, what the hell is the large black plastic vent like part numbered 62940-32010 that sits below the lamp sensor box? Is this some kind of vent for exhaust fumes or what? I can't figure it's purpose.
Thanks!
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When your passenger compartment heater A/C fan is 'on' - the air entering the passenger compartment is eventually forced through small openings in your rear parcel shelf. The vent pipe you saw ducts the exhaust air coming down from the car rear parcel shelf out below the driver rear fender. This eliminates the problems you would have (in colder climes anyway) of having warm, humid passenger compartment air entering the trunk and then condensing on the cold metal of the trunk - leading to pools of water and ... eventual... rust.
I have had a number of problems with my lamp warning sensor over the years. My garage mechanic kept suggesting I just take a 1" X 1" piece of black electrical tape and use that to cover over the warning bulb on the dash. That is likely the easiest solution - however I would not listen. Come to think of it - My wife tells me I never listen. I digress.....
To resolve poor ground I started by running additional ground wires from the trunk lid to the car frame. That did not help!!
What did work for me (for 99% of the time) is replacing the bulbs with the "higher quality" bulbs (longer life/heavy duty - whatever). I lightly sanded the bulb bases and the inside of the bulb sockets then lightly coated the bulb base with dielectric grease to ensure better base to bulb electrical contact.
I occasionally still get the warning light after going through a car wash .... no luck in spotting any water leaks - although you would think that would be the cause. After maybe 1/2 an hour the light goes out and I am happy... until the next time....
Hope this helps

wiring,
I'm
the
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What did work for me (for 99% of the time) is replacing the bulbs with the

coated
You can use more dielectric grease to help seal the socket from moisture entering and not hurt anything. It is non-conductive so more is good to a point. Don't put so much or get it so close to the glass on bulb it will/could run into reflector due to heat from the bulb. This might help but, any dielectric is better than none.
--
Hope This Helps,
davidj92
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Thanks, guys. I'm not sure what the quality of the bulbs I bought is. I got them at Pep Boys. I'll see if there are any better quality to be found and try that grease. Do you buy that dielectric grease at an auto parts store as well, or is that Radio Shack type thing?
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You can get it at the auto parts store. They also use it for spark plug boots etc.

found
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