sredmyer Posted June 11, 2017 Share Posted June 11, 2017 My underhood and trunk lights are not working in both of my cars. I think I understand that the lights for the trunk and under the hood are activated via a mercury switch that is somehow built into the light fixture itself. Unfortunately, I can't see anything on the light fixture that looks like it might be a mercury switch so either I do not have original light fixtures (possible but not likely) or I just have no idea what I am looking (MUCH more likely). Does anyone have a picture of one of these lights sowing the mercury switch? Quote Link to comment Share on other sites More sharing options...
72-CLASSIC_RIDE Posted June 11, 2017 Share Posted June 11, 2017 The Mercury Switch is encased and built into the body of the lamp housing and yes, both trunk & Hood Lamps have Mercury Switches. Sorry, don't have pic's but had installed a second Hood Lamp a few Months ago. With the Hood up, see if your getting power to the Lamp Assy using a simple test light. I'm guessing it isn't the Mercury Switch that's the problem. The possibility of the bulbs burnt out is also more likely. Doug Quote Link to comment Share on other sites More sharing options...
Rob Peters Posted June 11, 2017 Share Posted June 11, 2017 You won't actually see the Mercury switch because it is completely encased into the housing. The lights get their ground from being attached to the hood or trunk so you could clean up those connections. With a volt meter set to read DC voltage, raise the hood or trunk and remove the bulb. Connect the voltmeter black lead to a good ground point on the car and touch the red lead to the silver or brass spring loaded contact recessed in the lamp socket. You should read 10 to 14 volts. rob Quote Link to comment Share on other sites More sharing options...
sredmyer Posted June 11, 2017 Author Share Posted June 11, 2017 Thanks everyone. The hood light issue turned out to be a blown fuse on both cars. There is actually an inline fuse in the power wire which connects to the horn relay. The trunk light in one car was just disconnected (not attached to the trunk) so it wasn't getting ground. The other car just has a bad bulb in the trunk. Quote Link to comment Share on other sites More sharing options...
MCfan Posted June 12, 2017 Share Posted June 12, 2017 Glad you were able to solve your hood and trunk light problems so quickly, Steve. That in-line fuse for the hood light is a good place to disconnect the light if you need to leave the hood up with the battery connected for quite awhile. I often leave the hood of my SS up while it's parked in the garage to discourage any mouse that slips into the garage looking for bird and deer feed. Those mercury switches are really mysterious. I bought a complete set of courtesy lights including the hood and trunk lights from Murphy a couple years ago and installed them in my 4-speed car. I studied those bulb sockets, the assembly manual and the wiring diagram in great detail because I had to build my own wiring harness and I never could figure out how those two bulbs were switched on and off. They worked like magic, it seemed, and then I read somewhere that they had mercury switches. I put a bayonet connector in-line for the hood light on that car, not realizing that the factory harness had an in-line fuse. Guess I'll add an in-line fuse also when I get back to FL this winter. How's your move into your new building going? 1 Quote Link to comment Share on other sites More sharing options...
sredmyer Posted June 12, 2017 Author Share Posted June 12, 2017 Thanks Dennis. Progress on the building has been painfully slow. I think the guy doing it just over committed himself this summer. Quote Link to comment Share on other sites More sharing options...
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