Yes, I did go over that circuit for my 72. The things I remember are that flasher has to have the correct load or it will not "oscillate", so if you test on the bench you cannot test with a voltmeter only. There were two version of the lighted switch I think. In any case the switch is important as it transfers the 12V through it for the turn signals when it is not depressed and that had failed in mine. I believe you can test the circuit including the switch with an ohmmeter and you should test the flasher voltages at the flasher relay. No turn signals and no hazard signal? That should be easy. Either 12V, ground, or the flasher itself are candidates.