I had a problem with the light switch on my 86 fc3 na so I went to the junkyard and got a new switch and wire harness...Two weeks later I'm back to square 1 no running lights.....I checked fuses and relay seem to be ok....Then the other day I was working on the fuel system and I had just turned the key on to acc and there was smoke coming out of the dashboard! WTF? Has anyone else been through this? Can anyone offer any advice?

 

Burning out of the light switch or light switch harness is generally caused by poorly maintained lights.

Most noteably are the bulb sockets. Often when bulb get changed or if a seal fails, most owners fail to use some conductive grease on the bulb or bulb socket. As soon as corosion builds up from a leaking seal or bad bulb connection, it puts an extra load on the light switch and its wiring.

The second reason for a light switch burning out would be that the switch itself has cold solder joints.

As a reminder you never ever want to use a new, or rebuilt light switch with an old damaged harness. The resistance will be too high on the connection and cause the same thing to happen again.

So, to make sure the problem does not happen again:

#1 get a new or rebuilt light switch, not a junkyard one.
#2 put conductive grease on all the bulb sockets.
#3 use a undamged light switch harness.
#4 use a relay on the parking light circuit (covered in the archive section of this board).

And I do have the relays as well as rebuilt light switches available on my webstore.