I replaced the multi switch on my 98 blazer and my left tun signal is still acting crazy. The left turn signal works until you mash the brake pedal and then it makes a buzzing in the flasher behind the glove box. You can take your foot off the pedal and it works. It's only the left turn signal any help would be greatly appreciated.

 

Corrosion and/or wiring problem at the left rear tail light?

 

I dont see any corrosion and it seems to be wired the same as the right side. I cant figure out why it works until you mash the brake pedal and why the flaser seems to vibrate so bad it wants to jump out

 

could there be a short in the trailer wiring harness someone has put a 7 pin plug on it? sorry about that I'm trying to figure it all out. THANK GOD, that was it I'm blinking again!!!

 

It is definitely possible that someone has improperly wired the 7-pin connector. There are diagrams posted for the trailer plug and your owners manual details the wiring as well.

BTW, please edit your post if you have additional information to include. Rules are rules.