97 blazer turn signal problems

have a 97 blazer that when you turn the left signal on, with the headlights on, it does not blink. Head Lights off it blinks dim on both sides, like it is shorted or something. THe interior lights will then go bright and dim like the blinker lights. What might be the problem? If it is the switch can I repair it myself? Thanks, Dan

Bad ground or bad wiring or bulb socket do a lot of strange things like feed back on other stuff.
Check for good ground.
MT