This sounds like a bad flasher or bad flasher hook-up or wrong voltage flasher, check that first. You can pull flasher out of it's socket and touch two of the socket terminals together to see if a front and a rear bulb comes on when the turn sig lever is in correct position, as if you are the flasher. This will show if a bad flasher is a fault, If not, Then proceed with testing. This may all be obvious but: Using the tail lights as an example, there will be three wires going back there (you may have others for other lights), one is split and goes to both lights (this split wire is your running lights and brake light), the other two are your turn sig left and turn sig right. Resulting in two wires to each socket. If this is what you have, then be sure they are wired to the turn sig switch properly. Now all the rest is just a hot test with a bulb type tester. if the tail lights work I assume the bulbs are good, don't think all four would be bad. So, turn lights on, take out bulb, touch tester to one contact down in the socket and touch ground with wire end of tester, no light? touch other contact, should light. Now you know which is run and which is turn contact. Turn off lights, turn on key and move turn sig to the direction of the bulb you are testing and check contact to see if your test bulb blinks. No voltage? follow wires backwards checking the next place it is terminated to something (turn sig switch, fuse box, connector, terminal block) and keep going till you find voltage. This is the way to trouble shoot your installation rather than random checks of various places. Methodical, backwards, hot check. You will find voltage eventually and then you know the problem is between the voltage and the bulb. Things I don't know: What kind of turn sig sw you bought, if it's used or new, does it work, did instructions come with it, do you have two-contact sockets, do you have two-filament bulbs, are you mixing 6V and 12V items.
