MX-5 Miata

Remove climate control unit. Check continuity between rear defogger switch connector terminals 3B (Gray wire) and 3D (Black/White wire) with rear defogger switch on. If continuity is present, rear defogger switch is okay. If continuity is not present, replace rear defogger switch.

Fig 1: Identifying Rear Defogger Switch Terminals (MX-5 Miata)

Courtesy of MAZDA MOTORS CORP.