Thanks Steve and Dave. So if I run a wire from the R rear to the "brak wire" on the L rear, it should work? Because the
L rear does work. (Both front signals work.)
Is this solution correct? Thanks, again,
No. Not if your system is wired as most are and the brake lights are fed from the directional switch. If you did that then the right light will flash with the left when you put on the left directional. The 7 wire directional switch should be fed with a hot wire returning from the brake light switch. There should be four other wires to make all four lights, left front, left rear, right front, right rear, flash as directionals. The other two wires are for the flasher. A 8 wire switch has a ground so the switch body doesn't need to be grounded firmly to the column.
The left and right rear, when the brakes are depressed, are both fed through the directional wires. If a direction is selected on the switch, then one light will flash and other will work as brake until either the brake is released or the switch shut off.
Reading your post it sounds like you might have separate brake light system though. You did say that the right directional is working and running light on the right is also working if I read it correctly. If that is so, and your brake switch is NOT feeding your directional switch, then you could connect the left and right BRAKE light wires together. The brake light bulbs should be single filament bulbs and in actuality, should already be connected together.
I'm editing this because I read your post again and you say the regular light works (running lights I assume) and the signal light (directional) works on that side. Do you mean both the front and rear right directional lights or just the front is flashing, not the rear? I can tell you that I have an 8 wire switch that fails to flash the left front when using the hazard switch. This is a failure in my switch. When using the directional lever, both front and rear directional lights work on both sides, so speaking from experience, yes the switch could be bad. It depends on the above I mentioned.