I don't own a Packard but this is the only site that had the info for the flashers and schematic that led me to replacing the transistor for mine So I thought it polite to share the info.

For all you Napa 535 users. I opened one up and removed the pnp 9012 transistor and replaced it with a NTE electronics npn 123ap transistor.package reads nte 123ap t-npn,si,amp,amp to vhf sw. (Compl to nte159) this is a to92 style replaces ecg123ap,ge-123ap,sk3854 My signals and pilot lamp on my 50 Dodge Coronet which is a pos grnd system now work.