I have a Wesbar low profile trailer light and recently replaced the waterproof capsule because of two problems. 1.) small bulb that serves as a side light had burned out and 2.) The trailer turn signal on that side would not work. Problem 1 solved but I still do not have any turn signal. Both signals on the tow vehicle work fine and the left side trailer works fine. Any troubleshooting ideas? I'm stumped. I know any trailer shop can fix the problem but it seems so simple that I thought I could do it myself. Midwest stubbornness. Thanks

Clean the plug really good.  That contact may have some corrosion.  Also check the wiring for a loose wire.

....."but it seems so simple that I thought I could do it myself." Yea right . How many times have I said the exact same thing. If you don't have a light tester get one and start from the truck tail light and work your way down the wire to the trailer tail light. You should find the short. Good Luck.

check your ground wire, make sure its tightly hooked to both the trailer and Truck

I had the same thing happen.  

First I used a light tester and started at the tounge.  After finding ample powere there I moved to the back of the swing away tounge.........nothing.  I pulled the wires out and that is when I found out that the wires had been cut due to me backing up into them or something.........when you hitch up yourself this is a common problem.

However I still wasnt getting any power to the rear lights after fixing that problem........so i had to start the process all over again.......I still wasnt getting power as far as the back of the swing away tongue.

I found out that I was losing ground at the pin that hold the swing away toungue in place.  So I simply regrounded it.

So check all grounds, and check for damaged wires........especially close to the tongue.

I had the same problem as you are haveing. but mine quit working on every trailer I had. Come to find out it was my truck I have a 2006 Dodge 3/4 ton 4x4. it was an electrical module blown . Dodge replaced it under warranty and no more problems after that. If i were you go to Lowes are your locale hardware store and get a electric tester they make one you can ground on your vechicle and just stick the point ont your wire if it light you have power move down the line untill you have no power. But start at the truck with no trailer hooked up test the truck then just your adapter then the trailer. hopefully its something very simple. GOOD LUCK

Not the ground or you wouldn't have any lights: It's the brake/turn wire - find the break and you are good to go when you fix it.

If the light on one side does not work at all, your problem is mostlikely a bad ground. If the light works but not for all functions, you mostlikely have a bad wire or bulb. I have had so much trouble with older trailers that I now run a dedicatedd ground to both lights and have had no further problems.