Cadillac Repair: Directionals, turn signal switch, left turn signal

Question
My left rear signal is not working.  All the bulbs are good.  I changed the flasher but that didn't work.  All the other lights work.  The tail lights, the brake lights, and the 4 way flashers work. One thing that I noticed is that when I put the signal ont he left side the flasher flashes really fast.  It's normal on the right side.  All the bulbs are good all around  I'm lost.  What can I do?  

Thanx for you help

Answer
Hi Paul, This is a strange one. From what you indicate, when you put on the left turn signal just the rear bulbs fail to light up. But when you put on the brakes or the hazzard lights those lights now work or do they still stay off. Knowing that would be a big help.

     When one side blinks faster than the other with the turn signals on that usually means that there is a bulb out, you have a wireing problem or the bulb socket is bad. The flasher controls both sides so if both acted the same then it would be a problem with the flasher.

     In order to help you out I will need to know if the bulbs are always out or they work in hazzard mode or with the brakes on. Also what year and model Cadillac do you have?

    One other thing you could try is remove the bulb(s) from their socket(s) for the bulb(s) that fail to light. Then put the LH turn signal on and see if you are getting battery voltage on the center terminal with the key on. If not then you will need a wireing diagram to trace the circuits back to the turn signal switch to find out where the power stops. It very well could be a bad turn signal switch especially if the brake light works but the t/s and hazzards don't. If you do have power then check for the ground circuit being open. You would need to find a power source and place you positive/red meter lead there while you touch the side of the bulb socket with the other/black lead to check for the ground circuit being good.

    Let me know if you need more help. Bill