"642" Flasher Won't Work

[Joe M.]

I own two 642 parking brake flasher units, both of which worked until this week; one was a NOS flasher. I removed the back plate and studied the internal parts. Both allow 12V to pass straight through so the bulb lights up, but won't flash.

I think know what is suppose to happen inside the flasher to make the on/off cycle, but don't know how to make that happen now. I made a sketch of the internal part of the flasher. The on'off cycle works one of two ways,

1) when 12V is applied the thin metal ribbon (bimetallic strip?) heats up and lifts up, breaking the circuit, cools and drops back down on the vertical pin; the stretched wire keeps tension on the metal ribbon, or


2) the stretched wire heats up, relaxes and that lifts up the metal ribbon, breaking the circuit, wire cools and ribbon drops back down on the vertical metal pin.


Either way, the wire or the bimetallic strip are not responding to 12V anymore. Can the original function of the 642 flasher be restored?

The quick fix is to use a #257 flashing bulb and retain the original look

[Joe M.]

Re: "462" Flasher Won't Work

Apparently I was dyslexic when I posted this. I am referring to a 642 Tung Sol flasher.

[Ruedi K.]

Re: "462" Flasher Won't Work

Hello, There is another thread about this https://www.forums.ncrs.org/showthre...e+flasher+work I don't know if they can be repaired, it seems difficult, so I bought a NOS for my Vette. Would be interesting to know, how to repair them.