Mercury or Gravity Switch

[73Steve]

Well I recently started replacing incandescent light bulbs with LEDs in my 1973 Mach 1, starting first w/a sequential taillight kit from Easy Performance. Then replaced marker lights, interior lights, front turn signals and headlights. I love crawling around this car and learning more about its flaws and quirks. Anyway, when I replaced the trunk interior light, I found it was wired thru the headlight switch and only comes on when you turn the marker lights or headlights on. No problem, I need to run a positive lead from the fuse block to the trunk anyway for the sequential taillights. Did these cars come with mercury switches under the trunk lid for the trunk light? I’m sure they sell more modern versions of these switches since mercury is deemed to be dangerous. Any clues as to sources for these switches? My 71 Torino had the old style mercury switch. Your help is appreciated.

 

[Doug's 73 Mach1]

Original trunk and under hood lights used a mercury switch built into the light sockets. The positive wire on these was always "hot" connected to a 12V battery source. The light bracket fastened to the trunk lid or hood served as the ground connection.

 

[rackerm]

Here is an orginal and the mercury still works to turn it/off as the hood/trunk tilt.
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[73Steve]

Thanks for sharing the photo! Nice to know what it looks like and how it works!