Year and type and pix always helps.
If it's an SC, someone may have added a relay to reduce the load on the ignition switch.
Meaning: One of the yellow wires from the IS would energize the relay, which transfers power from the main starter terminal to the Solenoid post where the yellow wire would have been before the relay was installed.
The second yellow wire (for the cold-start circuit) stays on its usual Solenoid connection.
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1980 Carrerarized SC with SS 3.2, LSD & Extras. SOLD!
1995 seafoam-green 993 C2, LSD, Sport seats.
Abstract Darwin Ipso Facto: "Life is evolutionary random and has no meaning as evidenced by 7 Billion paranoid talking monkeys with super-inflated egos and matching vanity worshipping illusionary Gods and Saviors ".