I'm not real good at this stuff but reading your posts it sounds to me like a short in the wiring. since you say when you replace the turn signal switch things work right for a while I would start looking at the wiring in the area around the switch. double check any connectors to make sure they are not loose. check that the wires going into the connectors are secure. watch for any discoloration of the insulation on the wires in the area of the switch. if you find nothing move to the back and check the wiring going to the break lights/turn signals. Just my two cents for what its worth