Left blinker got fast, looked at the front, left front bulb was very dim. I figured it was on its way out. So I went and got some new ones.

Before I put them in it started to work normal(bright all filaments glowing normal blinking rate) again for a day.

Then it's went back to dim and fast blinking. I replaced the bulb and it still has only one filament lighting up, any ideas? I replaced the flasher (behind hazard button) 6 months ago. All other bulbs are working correctly

Thank you

 

You have a corroded connection somewhere. Most likely it is in the main connector at the back of the headlight housing. If not there, check all four tabs in the bulb socket. Using a small flat blade screwdriver slice a thin strip of 600 grit sandpaper folded over the end of the screwdriver tip to gently clean off the corrosion on the contacts. MAKE SURE THE POWER IS OFF FIRST. Be sure and use a glob of dielectric grease in the socket before you replace the bulb. It will prevent the contacts from corroding again. You can get a small packet of it for a few dollars at an Advance or O'Reilly auto parts store. DO NOT use "CK" type bulbs. Plain old regular 3157 bulbs are what is needed.