for reference just installed a new transmission in my 95 ex civic. tranny is from 99 ex.

okay when the headlights are off everything is great. when you turn the headlights on everything is great. but left headlight randomly turns off by itself and when that left headlight turns off the speedometer will stop working. then as soon as the headlight comes back on, speedometer comes back on. well???????

example: wifes driving with the headlights on, so lights are on and left and right light are working and speedo are working, then she hits a bump and the left light and speedo turn off. so shes driving and if she turns off the lights the speedo works if she turns them back on and only the right light is working then the speedo isnt working. then she hits another bump, bam left light turns back on and speedo turns back on.

speed sensor?!?! wiring?!?! possessed?!?!

 

A wire is grounding or touching the wireing for the speedo. Prob somewhere around the fure box area. Have you had any work done under the dash lately?

 

Yup, aparently this is a common problem. It happened it me last week in my 98 civic. Speedo just stopped and it was throwing a CEL code. So I took it in and they knew exactly the problem. Bared wire near the firewall. He told me it is more common then I'd expect. Hope it is of help.