GM Part Number 12450086 - lamp assembly having a gravity-actuated switch

Discussion in 'General Chevy & GM Tech Questions' started by PantheraUncia, Jul 15, 2012.

  1. PantheraUncia

    PantheraUncia Epic Member 5+ Years 1000 Posts

    In english, what this means is this GM Part is the Under Hood Work light that is in my truck. :) . What has happened apparently is that the gravity-actuated switch in this light fixture is no longer working for some reason.

    I have been google searching and been unable to locate a source that can confirm this part is what they say it is and order a replacement.

    Option 2 is to find a male pigtail that has the appropriate connector and just install a couple of waterproof 18 inch LED strips and forgo this lamp assembly (which was not that bright anyway).

    But the problem then becomes, how do I get it to power on the light when I open the hood and then shut the light off when I close the hood.

    Any suggestions?

    oh, here are 2 links to what I have found:

  2. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    No suggestions from me; I don't have an under hood light. I use a flash light for that. :)
  3. Crawdaddy

    Crawdaddy All hail the Mad King!! Staff Member 5+ Years 1000 Posts Platinum Contributor

    If I remember correctly, that lamp simply uses a ball that rolls back and forth and when the hood's up, closes the contacts of a switch to turn the light on. I'm not sure if you can take the light apart and free and lubricate the ball, but you might.

    As for a switch to automatically turn a set of LEDs on when the hood is opened could be done with a simple normally-closed pin switch or normally-closed magnetic switch, like one that's used in some household burglar alarms. There's also other ways to do with normally-opened switches, but they involve circuits with relays. For just a couple LED strips, I'd just run the lights straight through a switch with no relay.
  4. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Sorry, I can't tell, from your description, if you know for sure the switch is bad, or, if all you know is that the light is not working.

    Let me know, what you know, all of the pieces are very easy to test.
  5. PantheraUncia

    PantheraUncia Epic Member 5+ Years 1000 Posts

    Hi Ray,

    I went to advance auto over here and they had a guy that knew a little about electrical stuff so he brought out a volt meter and we tested the plug on the wiring harness (back to the battery) and we were getting 12.1 +/- volts at the plug. so we pulled the lamp ( not the bulb ) off the hood took it inside and tested the connections on either side of the bulb.... we got 12.1 volts there too. then we tried the positive and negative on the male pins on the lamp connector and it failed.....

    I saw the snaps around the case, but there are like 7 of them (some in odd places) and I was not sure how to open it without breaking the snaps. The PDF in the second link shows the diagram how it is built and the gravity switch.

    I guess I need to know how to open it and then what to do to fix it.

    Thanks :)
  6. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Ok, so it sounds like the switch and the bulb socket are one assembly.

    If you try to open it, you will probably break the plastic tabs (plastic gets brittle as it ages).

    If you want to have the OEM look, you'll have to get a replacement from GM.

    You sound like your not happy with the light from it anyway, so throw it away and go with the LED strip idea.

    You will need a gravity switch, I'd just google gravity switch and see what comes up.
  7. PantheraUncia

    PantheraUncia Epic Member 5+ Years 1000 Posts

    Cool Thanks Ray,

    I haven't looked up gravity switches yet, but I have been looking at the magnetic switches. I think the LED's would be brighter and provide a "white" light instead of the dimmer yellow light from the OEM bulb.
  8. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    I remember seeing a cool under-hood lamp (don't remember where), it had an extension cord built in, you could use it in the holder, or pull the light out of it's holder and move it to where you needed it.
  9. pmf608

    pmf608 Epic Member 5+ Years 1000 Posts

    The under-hood light in my '01 silverado always had this problem. With mine though, all I had to do was give it a solid hit to get it moving and it would turn on every time. Now I don't have a light since gm decided to get rid of them in 03.

    From what I've heard, the '88-'98 trucks had an under-hood lamp that was on a cable like that and could reach to pretty much any point on the truck for changing a tire, etc. I've also heard that they are very hard to find though because everyone wants them and they are a direct swap for the 99-02 version and easy to install in newer trucks

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