Under the hood LED install using mercury tilt switch

SO I've been wanting to add a dedicated circuit of super white LED's under the hood, I've seen a bunch here and elsewhere so that's nothing new, I want to have the power source connected to the posts underneath the terminals so that you can disconnect the battery cables and still have lighting under the hood. I was thinking of different contact switches and another member mentioned mercury tilt switches. Intrigued I picked one up and started screwing around with it. It seems like a little bit more of a challenge and I don't think I've ever seen anyone else do it. For those of you that don't know what a mercury tilt switch is, it's a tiny little glass cylinder with a drop of mercury and two electrical contacts inside one end of it. As the cylinder tilts, the mercury slides down and closes a circuit by contacting both contacts at once.

Mercury switch.



Switch installed inside of a gutted ball-point pen



Switch has two wires coming out of it, I installed the switch in one end sheathed by some shrink tubing to act as a shock dampener and ran the wires out the other end with more shrink tube on it. I heated the pen to cock it at angle that I will explain later.



The switch and LED's I got a Fry's Electronics but I'm sure you can find these online. The LED Cree bulbs are sealed in an epoxy resin for "splash-proof".





For the install I have 18 ga wire, 14 ga wire, zip ties, harness tubing and a butane soldering torch with lots of extra butane.

First was to prep and solder up the LED's I used shrink tube for each connection and a larger piece of shrink tube to create a 'boot' over the wires where it connects to the LED pod.







Now I had pre-cut the wires to about how long i think they needed to be to all solder at the same point to one larger wire, I could have daisy-chained them too but it would have taken longer (don't ask me how I know). The pods come with some 3M adhesive on the backs of them which came in real handy in holding them in place to drill the holes.







After mounting the pods with sheet-metal screws and being very careful not to accidentally drill a hole through the top of the hood, I then could mock up the wires to where they will run and then cut them all off at the same spot. I then uninstalled the pods and set to work on the 4 into 1 (4x18ga into 1 14ga), solder connections, with everything shrink tubed I then installed everything into the harness tubing. The trick was to have the pods sticking out of the harness tubes at approximately the right spots. I started with the longest run first, installed it back to the 4 into one and put a zip tie at the pod end to hold the tubing still, then I worked my way down to the shortest pod wire run. At each of the last three pods I put a zip tie on the harness tube to hold the pod in place but I didn't tighten the zip tie all the way so that I would have wiggle room when I reinstall the harness.
This is the finished harness ready to be installed, It long enough to go all the way back to the battery and all i have to do is fish the hot wire out of the harness at the point where I will mount the mercury tilt switch.



That's all I got down tonight, will finish the install and write up tomorrow

Ok, finally the stupid heat wave broke and I finished this

So, I mounted the lights back up under the hood and began to mount the harness tubing with 3/8 clamps and sheet metal screws.







When I got over to where the switch is going to go, I fished out the how wire and soldered the switch into it and tucked the extra wire back into the harness tubing. Now I had wired up the circuit with the switch and played around with it to see where the right "tipping" point would be for the switch to close. I figured out that the right angle would have meant that the pen would end up mounted at a weird angle so I bent the pen to around 22*, what I wanted was the lights to come on when the hood was lifted but not come on when driving up a hill or over bumps. The bend meant I could securely mount the switch and still get the angle. With the 3/8 clamps on the pen, it's snug but I can still swivel it in case i need to still get the lights to go on with the truck facing downhill.





Switch solders



ALWAYS fuse your circuits, no matter how small the amp draw!



I wanted the lights to stay on even if I disconnected the battery from the rest of the truck, not the most elegant solution but it worked perfectly, an electrician would know these as 1/2 inch conduit nuts.

(Yes that is a can of Monster that I used as a little platform to hold the wire )





Lights on and all is groovy.







Now I just had to wait another hour and a half for darkness till the final result! The pics are a little misleading, it's actually pretty bright, I was able to work on some other stuff without any other lights needed.







Oh and what was I working on waiting for night to fall?

Moar blue LED's this time I mounted two pods under the hood scoop for moar evil blue glow coming from the hood.



Everything on all at once and my alternator groaning under the strain




Come to the light!

At the end of my driveway 80 feet away

 

Nice.

 

Looking good!

 

Bumpity bump, finished the install

 

Looks good Chris! I like the idea of doing something so that if you need to disconnect the battery you still have light. Good going!

 

So when are you going to do the puddle lights? If it's this week, I want to come learn please?

 

Not sure if I'm gonna have the time before I go on vaca, might save that for the Mod Day

 

Ya but what are you going to do when it is -37.894 degrees Fahrenheit and the mercury freezes?
.

 

Ain't gonna happen

 

The front lights are reflecting blue, they do not actually shine blue as this pic shows.



Plus they are not on when driving. And that SHOULD make a difference.

 

If it's hella hot on Mod day, I'm going with you to BAMF. I can't be in 90-100 weather for 12 hours.

 

Bravo. If you hit the gas hard enough, do the lights come one?

 

Haven't driven yet, but how the heck would I be able to tell from inside the truck while it's moving by myself?

 

In the daylight, you'd never know. But at night - you might get an unexpected "close-encounters-dead-aliens-hidden-in-the-engine-compartment-glow"

Or, you could deploy an unneeded small child to hide in the engine compartment while you're running. No, that's cruel. You'll have to use a specially trained cat.

I better get off the internet before I get myself into trouble.

 

Kinda like the Cat idea

 

SWEET...very nice job on that! Gonna have to copy.

 

Wow, nice job! I really love all the lighting on your truck it looks awesome

 

Thanks Guys!

Oh ye of little faith!

 

Good stuff!

Question why the mercury switch? Considering the potential mercury contamination of the engine compartment after an accident?

 

Just wondering if the lights come on when 4wheeling and bouncing around over rocks and such?