The early 66 was add-on. The switch was in the glove box, the power lead was a jumper on the cigar lighter, and it connected via a pair of jumpers to the TS plugs on the column. Plug-and-play, straight up for a 65 addition. Later 66 was integral. This wiring harness is available new, but with no switch, the switch is not available new. Ford stocked the early and late switches well into the late 1990's, and since the early one had the whole wiring harness connected, it was perfect for conversion. They still turn up.

 

It does work and wired up just as described above.

 

Hope this reply helps other members on this question. Six Pictures. The photos uploaded are for the 1965 mustang original Emergency Flasher & Switch which mounts on left side of lower dash in the “D” hole. The orange with yellow stripe wire which is spliced to a faded blue with white stripe wire is used to connect to the cigar lighter hot wire, which is the Blue with White stripe wire main harness. The flasher unit is number 536 and is used for this application while the turn signal flasher is number 552. This setup is in my 1965 fastback with a scheduled build date of October 13th 1964. There is only one "D" hole stamped into my lower leftside dash instead of two because of the early production date. Later production cars had the two "D" holes at that location. The Emergency Flasher was an option for the 1965 year. In 1966 the feds stepped in mandating it as standard equipment so the location was in the glove box. Hope these pics help out and feel free to ask questions.
Dave V.
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