According to the Wiring diagram there should be a Purple going from the fusebox to the indicator stalk and then a purple/black going from the stalk to the horn. My horn is permanently live so that should narrow it down a from the fusebox.
On mine, when I had her, both of those switches were not doing anything. One now turns the fuel pump on (previously turned the reverse lights) and the other is for the rear fog light.
"Y mae dafad ddu ym mhob praidd"
1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10
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