89 Accord LXi Electrical Problem - Brake Lights

Newbie to the forum. I registered and searched for a couple hours, but have come up dry on this exact issue.

When I turn ON the headlights, the 3rd tail (brake) light turns on also (and stays on). When I press the brake pedal, the dash gauges/clock/shifter lights DIM, and the brake lights burn brighter (no noticeable dimming of headlights when I press brake pedal). With the headlights turned OFF, the side markers, dash gauges/clock/shifter light LIGHT UP when I press the brake pedal. 3rd brake light stays off when headlights are off.

Things I've checked:
- plastic stopper on brake pedal arm is intact (makes contact with brake switch like it's supposed to)
- changed the 3rd brake bulb
- checked all the fuses under the hood (and they look OK)

Possible culprits?
- brake light switch is bad?
- fuse under the dash is bad? (I'll check these next -- i don't fit very well under the dash)
- faulty ground or short somewhere? (yike$)

Any thoughts? I do not have any experience tracing electrical problems, not do I have a voltage meter, etc. for checking the wires. I never had the manual for this, so checking fuses is tedious without the diagram. I hate to take it to the dealer and have them poke around looking for an electrical problem for $60 an hour.

BTW, great forum. One of the few I've come across that isn't full of flamers. Thanks to all who contribute to help the rest of us!

 

open the trunk, on the drivers side find the wire harness that is near the trunk lid hinge. open the wire loom where it flexes and look for cracked insulation on the wires

 

Thanks, 'dude'. I crawled in the trunk and fished around the wiring harness by the hinge. I did, in fact, find a broken wire -- about 10 years ago, I closed the trunk and crimped a wire back there, causing one of the tail lights next to the license plate to go out. My mechanic (the guy was a bit of a tool) said it would be easier to disable the corresponding light on the other side than to trace the wiring to find the cause. I took his advise and disabled the other light, and have lived without them for years (the other tail lights have worked fine). Well, I fixed the wire and both tail lights now work.

Bad news is... my center brake light problem still persits. I then crawled under the dash to inspect the wiring, and discovered the #15 fuse was missing altogether. I'm thinking "hot damn, I found it!"... I replaced the fuse and... crud, no change. Brake light problem still persits.

I also checked the wiring harnesses for the front headlights, thinking 17 years of opening and closing may have cracked the insulation. Could not fine anything suspicious, though. My next step will be to check all the fuses under the dash one-by-one. I also realized my cruise control does not "set" (I drive mostly in town and rarely ever use it). Could this be related to my brake light issue?

A couple questions... 1) there is a wiring harness piggybacked on the brake switch harness with a pink and a black wire -- what's that for? and 2) can somebody post a diagram of the dash fuse box for an 89 Accord LXi?

Thanks again for the help.