Suddenly, the turn signal flasher unit in my 1955 Coupe stopped working.
Failed electromechanical turn signal flasher
A slightly premature post-mortem examination revealed that a tiny spring supplying proper placement for one of the bimetallic strips had collapsed rendering the unit inoperative. An adjustable harness made from fine wire restored operability, but with a slightly different flashing cadence than previously.
Electromechanical flasher with fine wire spring
Several weeks later the unit stopped working again making it the obvious time for a more permanent solution, but this was complicated by the fact that the original flasher unit had been substituted by the first owner of the car (sometime prior to 1964) and that I did not wish to disturb the somewhat fragile wiring harness so as to return to the original configuration. Hence, I was faced with the task of adapting a modern flasher unit to fit within the existing canister to mate up with the female connecter as installed on the harness.
Several trials with modern flasher units (I didnâ€™t realize there were so many) resulted in no activity whatsoever, the blowing of No.5 fuse, or an unacceptably rapid flashing rate depending on how the wires were connected. Research indicated that these units all had a â€śbulb outâ€ť sensing circuit that would produce a rapid flash to indicate an inoperative bulb and that the load created by the Coupeâ€™s standard two bulb system was not sufficient to overcome this modern day safety device.
Research on the Internet revealed www.autolumination.com Tail Light Brake Light Turn Signal LED Bulbs
which advertised an EP34 (CF13JL-02) unit sporting the proper electrical connections and designed to restore a proper flash rate regardless of incandescent or LED bulb use or any mixture thereof. $14.99 plus $4.00 shipping plus four day delivery time from Arizona provided me with a generic appearing flasher labeled only â€ś0431â€ť which when temporarily wired into the car worked perfectly.
Electronic flasher with steady flash rate for incandescent and LED bulbs
To provide the proper connection to the existing wiring, I dismembered a standard Mercedes-Benz relay (001 542 02 19) and soldered wires to the appropriate pins to provide the needed â€śBâ€ť (+), â€śEâ€ť (-) and â€śLâ€ť (Load) connections. Since there would be insufficient room within the old canister to allow use of push on wire connectors, the flat spades on the flasher unit were drilled and tapped for 6-32 screws and the wires attached accordingly. A new base plate was fabricated from sheet plastic to mount the reconfigured relay base and to seal the bottom of the canister. This base plate was attached to the relay base using ethyl cyanoacrylate glue.
Flasher on the left and â€śdonorâ€ť MB relay on he right with the proper base pin configuration.
Relay base with wires attached, the electronic flasher with tapped holes and screws, and the round baseplate to fit the electromechanical flasher can.
The electronic flasher wired to the â€śdonorâ€ť base with the round baseplate attached.
Finally, to eliminate any chance of shorting caused by internal movement, all connections were covered with Liquid Electrical Tape and the inside of the canister was insulated with a portion of the central cardboard tube from a roll of toilet paper (several attempts were required here as these tubes come in slightly different diameters). The completed assembly was installed in the canister using clear silicone as an adhesive/sealer resulting in a unit visually identical to that with which I began, but one that functioned as intended.
Assembled replacement flasher with insulation applied to the internal connections.
Assembled flasher contains state of the art electronic flasher with no change in appearance from the electromechanical flasher.