2002 Express, 12-passenger van, original condition. Engage turn signal and that side will blink very quickly. At the same time, the other side will dimly blink in unison. From the outside, it almost looks like the hazards are on. Sometimes, the gear select indicator light will blink in the opposite. Sometimes, the system seems to work fine, other than the fast blinking condition. Any ideas?

 

Usually the fast blinking is an indication of a burnt out bulb. It could also be a bad connection in the socket and not making good contact with the bulb. Loose or broken wires. Look for all of them.

 

Ditto. The brake filiment is broke off and touching the parking light filiment inside the bulb,,or something like that.

 

I did a walk around, all the bulbs seemed to be working. I'll try just replacing all the bulbs & cleaning the sockets while I'm in there. It can't cost that much. Thanks for the tip!!

 

This thread is old I see but thought to write a response anyway.
I recommend checking your body ground, often times when weird
electrical problems arise it a ground issue.

 

The grounds on the Express Vans that come off the battery, go to the block, and have a woven copper strap to the body, go bad in the snow belt. The gauge cluster usually starts tweaking first in my experience. Give that ground a good look if you're still having issues.