Speedometer on 97 Civic lx stopped working last night after I drove through some rain water. The headlights would get bright and dem? What could this be?

Check alternator fuse!! if its blown....

under the intake manifold at the rear of the engine there is a pack of wires. This pack rubs on the bottom of the intake and creates a short circuit which screws up the !!speedo!!, sets off the check engine light and gives a trouble code (if you know how to read the check engine flashes) that there is a problem with the O2 sensor, and sometimes the headlights would surge.

Just crawl under the car when it is up on stands and gently turn over the pack of wires under the intake to expose the bare wire or wires. Tape them up and away you go.