Front right drivers side turn signal stays on when vehicle is off.

SOURCE: electrical problem

Find the ground wire on one of the lights and add another ground wire to a good clean metal surface and see if that fixes the problem. It defently sounds like a ground problem at one of the lights.

SOURCE: 2001 chevy silverado 1500 v8 battery drain after sits for 1or2day

, do a simple test on the charging system...check battery voltage. should be 12v or better. start engine & check volts at idle, no accessories on. volts should read 13.5 -14v. Turn on all accessories(including headlamps on high) volts should drop slightly but should not creep down. Definitely not below 12.5. If voltage drops lower than 12.5, the regulator (in the alternator) is not working. either change regulator or change entire alternator. Alternator drive belt should have sufficient tension so that alternator cannot be turned easily by hand. If it can, check belt tensioner.

SOURCE: 93 S10 left turn signals not working

Have you tried replacing the flasher? You'd think neither side would blink if the flasher was bad but I've seen this happen and it turned out to be the flasher. You could swap the signal flasher with the 4 way flasher to verify that's the problem before going out and buying one. Should be a few bucks at the parts store.

SOURCE: 2005 Tahoe Z71: My battery died but was able to

When your battery died, it probably wiped the PCM memory. Drive for 20 minutes in stop and go traffic then 10 minutes on the highway to reset the PCM sensors. Check to see if this helps at all. It's wierd to think about, but the PCM can control alot of the systems in the A/C.

SOURCE: 2003 Chevy HD trailer wiring problem

I have the exact same issue. I have also tested my trailer on other vehicles and it works fine. I even purchased a light up tester and found the problem at the harness. It seems like a bad ground to me but I can't seem to find one.

The trailer lights have a common brake/turn wire while the truck has seperate turn and brake lights. I think the problem lies with the device that marries the two for the trailer wiring but I don't know where to find it?