Author Topic: Left Turn Signal Issue and Resolution  (Read 1298 times)


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Left Turn Signal Issue and Resolution
« on: May 05, 2022, 09:26:55 PM »
The moral of the following is to always check the simplest thing first.

Back in the summer of 2018, I converted the majority of the lamps/bulbs in my '69 RS to LED.  This included the:  headlamps, interior dome and console courtesy bulbs, the side marker bulbs, rear turn signal/brake bulbs, and taillight bulbs.  I did not convert the front turn signal bulbs but left them as original; i.e. the 1157NA filament type bulbs so that there would be enough circuit resistance for both the mechanical turn signal and hazard flashers to function properly.

Everything worked fine up until a short time ago when the left turn signal began to flash slowly (with the engine running and the charging circuit at 14.4 volts) or not at all with the engine off (battery voltage at 12.5 volts).

My initial thought was that the front left turn signal bulb (1157NA) was bad.  I removed the bulb and the first thing I noticed was that both filaments looked good.  I checked the bulb for continuity between both button contacts on the bottom and the outside of the bulb and confirmed that the bulb was indeed good.  Since I had a spare bulb, I changed it anyway.

Still had the same issue.  With the engine running - left turn signal slow flash; with the engine off - left turn signal no flash.  Additionally I noted that with the engine running it was only the left rear turn signal (LED) that was flashing.  The left front (1157NA filament bulb) turn signal was not flashing at all.

Keeping with the thought process of check the simplest things first, I removed and reinstalled the hazard flasher (on the fuse box).  This had no affect - I didn't expect it would as this was the hazard flasher and not the turn signal flasher.  I then removed the turn signal flasher (which is secured in a clip on a brace under the dash in the vicinity of the ash tray/lighter) and reinstalled it.

Well, I'll be.  After removing the turn signal flasher and reinstalling it, everything works just fine.  I have no idea why this made a difference.  The flasher was securely installed in the harness before I removed it.  Additionally, since this obviously is not a digital system, "re-booting" a mechanical flasher shouldn't have changed anything - but somehow it did and at this point, I am not going to question the result or dig any further in an effort to grab defeat from the jaws of victory.

I have included a picture of this circuit for reference.

Just a FYI story.

Richard Thomas
1969 RS