Let me "splain" it this-0-way...
At issue (90-92 C4s) was the high current draw through the clutch safety switch necessary to operate the starter solenoid in the 90-92 circuit design. Arcing increases with current, and the clutch safety switch can't handle a steady diet of it!
So, in 93 the circuit was changed by installing a heavy duty relay to service the solenoid. As result, the clutch safety switch now only has to carry a very small current - just enough to activate the relay: the
relay now carries the relatively heavy current load required by the solenoid.
The relay modification (addition) to the 90-92s essentially updates the starter circuit to that of the 93+ C4s. The life expectancy and reliability of the clutch safety switch is thus vastly improved.
DIAGRAMS (BELOW)
- The 90-92 starter circuit schematic vs. the revised 93+ starter schematic.
- For the relay mod, the purple wire from the clutch safety switch is cut an connected to the actuator coil of the relay. A wire from the battery is connected to one terminal of the relay contacts and the other side of the contacts attached to the purple wire leading to the starter.