Underhood light switch

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Animal Lawyer

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My car has an underhood light socket but the way it is wired it is constantly hot. I am assuming there was supposed to be a switch that turns it off when the hood is closed? Does anyone have a part number (and any idea of who might be selling replacements) and a schematic (or even better, could take a picture of the switch and wiring? 

 
I do believe that they are a mercury type switch.  Constant power to the unit but only has a ground once the hood or trunk is open so far.  I'm for sure someone else will very or correct what type it is.   

 
You should be able to remove the light from the hood and turn it off and on by tipping it back and forth. If its original, it could be that the contacts are now always connected and probably needs replacing.  My original was doing the same thing and it was replaced by one of these. Fasten to the hood and feed the wire down to the fender area where its connected. You should see it turn off as the hood is lowered even before its closed all the way.

https://www.npdlink.com/search/products?search_terms=trunk%2Blight%2Bassy%2Band%2Bextension%2Bwire&top_parent=200001&year=

 
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The truck light works the same way.  Integral mercury switch.  Older home thermostats work this way too and you can see the mercury in the glass bulb make contact with the wire tips when tilted to turn on the heat.  I believe for environmental reasons, mercury switches are no longer produced for most applications.    

 
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