On my 99, when I use the left turn signal, the 4-way flasher comes on! At first it was occasional, now it's every time. I replaced the flasher relay---no help. Whaddya think? Bad turn signal switch> Bad flasher switch? Other?

 

Bad ground at one of the lights is backfeeding into the other system. Just a guess!!

 

Reminds me of an odd thing that happens on my WJ when it's really cold outside (like around freezing or lower. Sometimes, but not every time, when you use the turn signal, the wipers activate like you were using the washer function. (No, I'm not accidentally hitting it either.) It's repeatable about every 3rd or 4th attempt. After it warms up inside it stops doing it. I just chalk it up as a lovable quirk and live with it.