Virginiafiretruck,
I would guess these lights are not tied to any turn signaling device, but are a whole separate circuit just for emergency flashing. I wonder what made them flash in '52? Did the Tung-Sol style bi-metallic flasher exist then. I'm not sure on this, but I think a adequate sized flasher in series between the load (lights) and power would probably make them do their thing.
Fire engines have some strange stuff on them, so don't hold me to my word. I don't remember if your rig is still 6 volt, or has been switched to 12 volts. If a little flasher ends up being the ticket, you will have to find one that is the proper voltage and one that blinks the load at an acceptable rate. 6 Volt HD flashers might be a hard thing to scare up.
Is there some strange electrical box on the rig that might have been a motorized flasher. On an old fire engine, this would make more sense to me than a little bi-metal can! Dig around some, I'll bet you'll find a magic motorized flasher.
Stuart
