Narrative:

Cruise flight 70 NM from [destination]; a passenger alerted us that he saw smoke coming from the left circuit breaker panel. I looked down and confirmed that there was in fact smoke coming from the panel. Performed memory items and referenced QRH. [Advised] ATC. The isolation of the electrical systems stopped the smoke. We diverted to ZZZ (~40 NM) as it was closer than [destination] and would have emergency response crew. Landed at ZZZ and performed emergency ground evacuation per the QRH. Fire crews inspected the plane and were not able to find source of smoke but did detect a strong smell of a previous electrical fire. I suspect the source of the smoke was from the heater and or heater fan which was turned on 15 minutes prior; or it was possible it was the lightning strike detector. No circuit breakers or switch breakers were tripped. Aircraft was fresh out of phase; perhaps functional check flights after phase could prevent this experience for passengers. These passengers were on the previous flight which had an air return for a rough running engine.

Google
 

Original NASA ASRS Text

Title: Cessna 402 Captain reported that a passenger noticed smoke coming from a circuit breaker panel. After confirming that an electrical problem did exist; the Captain elected to divert a suitable nearby airport.

Narrative: Cruise flight 70 NM from [destination]; a passenger alerted us that he saw smoke coming from the left circuit breaker panel. I looked down and confirmed that there was in fact smoke coming from the panel. Performed memory items and referenced QRH. [Advised] ATC. The isolation of the electrical systems stopped the smoke. We diverted to ZZZ (~40 NM) as it was closer than [destination] and would have emergency response crew. Landed at ZZZ and performed emergency ground evacuation per the QRH. Fire crews inspected the plane and were not able to find source of smoke but did detect a strong smell of a previous electrical fire. I suspect the source of the smoke was from the heater and or heater fan which was turned on 15 minutes prior; or it was possible it was the lightning strike detector. No circuit breakers or switch breakers were tripped. Aircraft was fresh out of phase; perhaps Functional Check Flights after phase could prevent this experience for passengers. These passengers were on the previous flight which had an air return for a rough running engine.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.