i have a 95 coupe and my entire wiring system is completely screwed up. Everything from the cluster to the climate comtrol, to the headlights and tail lights. Everything works fine until i turn on my headlights, and then my tach, speedo, fuel, and temp gauges drop, and no gauge lights come on except both turn signals get stuck on, only one head light, one brake light, no climate control, and wipers only work when parking lights are on or no lights are on. the only thing that i changed is that i plugged my new horn into the original wiring, except for i added the show horn piece and followed the directions from the DIY page for a JDM steering wheel, horn works, but sound fades to nothing and all gauges drop as well. Any suggestions about where to start would be great.

 

sounds like you lost a ground when you did the horn install.

 

the problem started awhile ago though because i used to notice my temp gauge move aittle when i turned my headlights on or off, or moved the climate control. so it seems like a problem that started a few months ago, and this was the final kicker. i dont evern know where to look. i removed everything that i did when i hooked up the horn

 

I'd double check all your engine-chassis and battery-chassis grounds. This widespread of an issue tends to be grounding problems.