Connecting a 12V power supply to 4th brake light to test?
 

Hey there guys,

More questions arise in the quest to get my goddamn 4th brake light working like its supposed to. Now that I’ve discovered that connecting my 4th brake light to the 4th brake light harness blows my running light fuse, I cannot plug it in. So, Ive been told to ensure that all components of the light work properly by connecting it to a 12V power supply. Seems simple enough to most, however I need to understand what kind of power supply I need and how I go about hooking it up. Does anybody know how I can go about this and what power supply I need? As of now I don’t have a functioning reverse light which is a bit dangerous.

Thanks in advance for the help! Ill be monitoring the thread on and off to anewer any questions you guys might have for me.

Any 120v AC to 12v DC supply will work. Use test leads to connect the positive and negative leads as appropriate.
This or similar is a good choice to keep around for various bench testing needs. Just need to strip an old 12v cig adapter to use as a test plug.

https://images-na.ssl-images-amazon....L._SL1500_.jpg

If you're blowing fuses though, it means something is shorting out, so check the wires you're going to hook up with a meter first before connecting them and make sure they aren't shorted out inside the unit.

Cool, is there a cheap meter that I can get? Also, once I've tested the wires, how do I go about hooking it up to that power supply?

Oh, to test it, I'd just run a wire from the car's battery back to the light.

humfrz

Rad, if its this easy i may be able to do this sooner than I thought. Where would i connect the wire to on the battery? Since its a wire harness, would i just connect the wire to each wire within the harness to test it?

Thanks for your response!

Well, I'd suggest you connect one end of the wire to the positive post of the battery (the red one).

The other end would go to the lead on the light that is supposed to be connected to a hot lead from the car. I'm not familiar with that light so, I can't help you.

Make sure the light is grounded.

If the light lights up, that would indicate that the brake light is good.


humfrz

Does it blow the fuse immediately or once you do something to have one of the lights come on? AKA hit the brakes/put it in rev. so on.

When I installed it, the only light that lit up was the reverse light (as I havent spliced the running or brake light into the tail light harness yet) so that should be the only light working anyway. I believe the next time I turned on the car, the other lights werent working so that may have been when. I didnt notice for some time, though. Couple days if that.

Might I have to splice the wires together in order to stop the shorting? Could that be why the fuse blows? If I remove the other wires and keep the reverse light (which still worked even though the fuse blew for the other lights), could I just run that?

This is a Valenti 4th brake light, by the way. Along with Valenti tails if that helps

Splice what wires together? I'm not quite sure you really know what you're looking at with this. You may want to find someone local with electrical know-how to give you a rundown on wiring.

As an additional note, if there's a possible short, please do not hook it directly up to the battery. You need a fused line to protect it, otherwise incendiary events are possible :evil: