Underhood Light Switch Fix
 

This same light is used in many models over many years. Frequently they do not operate, the culprit in my case was the gravity switch. Check your bulb and for 12V power at the top of the switch before cleaning. If there's no power the problem lies elsewhere.

To clean the interior of the switch you will need: small flat screwdriver, pliers, razor blade, 10 mm socket(not pictured), volt meter, WD40 and canned air.
https://cimg8.ibsrv.net/gimg/www.che...8ea66cbf07.jpg

To start, unplug the light, take off the cover, then remove bulb and 10 mm bolt.
https://cimg9.ibsrv.net/gimg/www.che...862a82c4c7.jpg

The switch is the small bullet shaped brass piece with a copper pin inserted in the plastic cap on the bottom. Inside is a steel ball. When tipped into an upright position the ball contacts the side of the brass chamber and the copper pin, closing the circuit. Mine was corroded internally.

Pry up the switch from the top to remove.
https://cimg8.ibsrv.net/gimg/www.che...32a52fdc47.jpg

Using a razor edge and a flat screwdriver the copper pin can be pulled out partially, then removed with pliers.
https://cimg2.ibsrv.net/gimg/www.che...a50b4a4209.jpg

https://cimg3.ibsrv.net/gimg/www.che...5ae633625b.jpg

https://cimg4.ibsrv.net/gimg/www.che...028ef594e5.jpg

Couldn't get a good picture of the ball inside.
https://cimg8.ibsrv.net/gimg/www.che...04c5f18155.jpg
Kind of dirty, pic was taken in the middle of cleaning.

WD40 is probably not the best cleaning agent, it's what I had on hand and did the trick.
https://cimg5.ibsrv.net/gimg/www.che...a61016309a.jpg

Blast the residue out with canned air. I bent the nozzle up and held a shop towel around the bottom, there was a lot of fluid inside.
https://cimg4.ibsrv.net/gimg/www.che...d56936fb3a.jpg

Replace copper pin and put switch back in the housing. Check for continuity with ball in the bottom of the chamber. (Clean again if necessary)

Reinstall.

https://cimg0.ibsrv.net/gimg/www.che...ec8ba98be3.jpg

Zero Ohms means it's good to go.
https://cimg2.ibsrv.net/gimg/www.che...de57468949.jpg

https://cimg4.ibsrv.net/gimg/www.che...185ffe664f.jpg

what a contraption!!
 

once i got it apart i couldnt believe it was made here on earth!
i usually break plastic retaining clips on electrical connectors and this was no exception. i still cant figure how to remount it to the firewall.
never saw a light bulb like that in all my messing with cars and lights
corroded contacts cleaned with a tiny file still make intermittent contact.
ive decided to get a regular light socket and a switch. i would expect this thing to come on overnight and kill my batt!!
love my jeep but nix on this xxxxxxt!! like to meet the engineer who did this!!

btw the oddball gravity sw works fine!

Good on you! Submitting for write up?

Good write up.

Great thread. Going to check mine out later today when I go work on it. Eventually I want to add one of those GMC retractable under-hood lights. I found a video where a guy rebuilt one with LED.

You mean like this. I have not completed it yet though. Jeep light on left and the bracket from it with the GM light on the right.
Do you have a link to the video you mentioned?
https://cimg1.ibsrv.net/gimg/www.che...0baed62c7c.jpg

I though about replacing the OEM hood light with a LED. If I get lazy I will surely use this thread to fix my stock one. Thanks!

Interesting that this thread got revived. I replaced the stock one with a GMC retractable lamp and LED bulb this last week. It does have a switch like the one on the right in the above image, though I may wire the gravity switch inline with the new one so it will shut off when closed if I forget to flip the switch.

A recommendation for others reading this, use a small measure of dielectric grease on all contact points, inside and outside of the switch.

thanks for that
mine is out also, will check on it