I have 1977 Triumph Silver Jubilee last year i put a new wire harness along with a new blinker unit in. This year the directionals and rear brake light decided to stop working on me i went through the whole harness and bought a new switch can anyone help?

I don't know if you've gotten it fixed yet,but if not, I'd re-check all the connectors and the grounds. My Bonnie lights go nuts if the fender shakes loose and disrupts the chassis ground. Pat

Sounds most likely to be a grounding issue. To do a quick check, I use a six foot piece of 16 ga wire fitted with alligator clips. Attach one end to the GROUND side of the battery and touch the other end to the afflicted component. If it lights up you found your problem. Now for the fun!! You will likely find that there is no ground wire to your signals or your taillight assembly. Fresh paint, a bit of corrosion or what have you is really going to mess up your day.
1. If it REALLY has to stay original, take everything apart and ensure you have good metal to metal contact from the last grounding point you can find, put it back together and wait until it fails again; or
2. Eliminate the Prince of Darkness! Locate a trustworthy grounding location, I usually use A ground in the headlight or at the Zener mount. Make a simple wiring harness to run from the selected point to each mounting point of the signals and to the taillamp. Get a bit of dielectric grease and put a tiny smudge of it on each electrical connector and lightbulb. Go riding and never worry about bad grounds again.
Good luck