mine does something similar... when cold, or humid... the signal either left or right will blink so fast it sounds like a buzzer. all lights work. I left the car in my yard with a bad trunk seal for 5 years and accumulated some mildew and corrosion on most of the electronics. the radio stopped working, the a/c, the cruise and the odo. I am sure tons of other things will act up. if you have mildew evidence, you might want to start taking things apart and cleaning them.
John

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!