PA-32 pilot reported a landing gear indication problem during approach resulted in manual extension of the landing gear and a safe landing.

Narrative

During the planned second leg of the day; the exhaust pipe from the number 6 cylinder failed. In addition to the associated muffler needing replacement; the liberated exhaust gases melted wiring and damaged the induction air filter. The problem clearly manifested itself when the oil temperature gauge suddenly read full scale shortly after takeoff with an alternator reading of zero following. Returning to the airport the gear pump did not operate; the circuit breaker had popped and would not reset. Manual gear extension followed. However; the gear indicator lights did not turn on; their circuit breaker had also popped. Tower confirmed that the gear appeared to be down. Landing and taxi were uneventful. During the previous leg; the EGT gauge which had been previously placarded in operative by maintenance but was working intermittently; suddenly stopped working again possibly accompanied by a subtle change in sound. As engine operation was normal; this seemed like an issue for future attention; especially as the sound seemed to go away on approach. The EGT probe attaches to the number six cylinder so it is possible that there was a relationship. The routing of both the landing gear pump and the indicator lights through the same wiring bundle added uncertainty to the gear's status after the manual extension. In hindsight the gear 'unsafe' indicator may use a different circuit path and thus the fact that it did not illuminate when flaps extend may have been a clue that the gear was down.