You most likely will have two of them. One covering the frt brakes and one covering the rear brakes. This way air pressure from either end can trigger the lights. Start at the foot valve (treadle valve) and work down from there. Could have one or two wires on each switch, and most likely connected between the two switches. Did you try it with the wheels chocked so the coach won't move and the parking brake off. Some Systems are wired to turn on with either the regular or parking brakes on.
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