Limit switch for hood lights?

Anyone know of a good limit switch to use so my lights under my hood turn on when the hood is lifted up? Right now I just plug in the hot wire to turn them on. Not exactly ideal for turning them on when it's dark lol I could just put a toggle switch in somewhere but I'd still have to find that in the dark and I don't want it in the cab. Just looking for a small switch and if anyone has done this where did you put the switch? Thanks for any help!

 

a mercury tilt switch would work. There are also magnetic normally closed switched that would work, but seems people have better luck with the tilts.

 

Bingo...

 

I have never even heard of those. Pretty cool idea! But won't it activate going up steep hills? Or quick acceleration? The latter probably wouldn't be an issue in my 4 banger lol

 

Mount it at a fairly steep angle, so when the hood is all the way open it is just beyond level when parked slightly nose-down.
It might flicker a bit on very rough roads, but it's only going to be for a bounce and won't stay on. Big deal... nobody will see it.
A hill would have to be steep enough to match the angle of the hood when it's up... that's not going to happen even in San Francisco.

Back in the 60s and 70s when vehicles came with underhood lights, Detroit used mercury tilt switches to operate them.

Mechanical thermostats also use them... tilt switch mounted to a coiled bi-metal strip.

 

ya know I have one of these doodads under my hood from the PO. No idea what it's for. Figured something with the remote starter.

Anyway yeah like Rich said, no issues with tilt switch, im gonna do that mod soon. Magnet switches would work too, im tempted to try that option

 

If you want a simple switch, I installed one on the radiator shroud, always easy to turn on in the dark, and very discreet. I wanted a two-way switch though:
http://www.tacomaworld.com/forum/lighting/239480-engine-bay-led-install.html

 

Yup. For remote start. If you pop the hood with no key in the ignition after a remote start this guy pops and cuts the engine

 

Where did you find that switch?

That looks great! Barely even notice the switch is there.


I think I'll give the tilt switch a try. Thanks for all the help guys!

 

Have you considered this?

Normally closed (as in closed circuit = on), but when you press down (i.e. the hood is closed on it) the it changes to open(open circuit = off). It doesn't lock in position. Works like a switch on a refrigerator door.

 

That is more of what I was looking for! I couldn't find anything small that I liked with that concept. Thanks!

 

A regular pushbutton like that Radio Shack switch is not going to work.

#1 - Positioning is going to be a PITA... you'll never get it right.
#2 - Durability... close the hood 3 or 4 times and that switch is going to shatter.
#3 - Not waterproof.

The only thing that is going to work well is a regular old style door light/alarm pin switch, magnetic switch, or mercury tilt switch.

The pin switch is going to require drilling and access to the other side of the hole for wiring... and finding a good place to mount it.
The mercury switch can go anywhere on the hood. Magnetic switches are a little more involved than the mercury switch, but still easier than a pin switch.

 

Some downsides to the mercury switches:
1) They contain Mercury in a glass tube. Mercury is very toxic which is why you don't see them on productions cars, ever.
2) Rapid changes in direction or speed can activate the switch.
3) High changes is angle (such as side, up or down hill) can activate the switch. Even the high vibration of a good washboard road could do it. Imagine turning on & off your hood light several times a second for the duration of the road.

A mercury switch in a car is just a bad idea. That is why they are never used.

As for these particular switches, yes, these are light duty. However, they are the right type of switch for this application. I found them with a simple search. I was not looking for an ideal solution. I listed them to show the OP that such switches exists and these types of switches are a far better idea than playing around with toxic chemicals contained in a wafer this glass tube.

 

They were used for decades.
Yes, there are concerns about the release of mercury during an accident, which are frankly, overblown.
Mechanical home thermostats STILL contain mercury tilt switches.

Hell, we used to play with the stuff in the 60s.

As far as actuation during changes in direction, rough roads, or incline... so what? It's an LED light under the hood... it's not an industrial safety device that is going to shut down a production line. Nobody will ever know if the underhood light flickers a couple of times when you hit a bump while climbing a steep hill.

Again... it's a non-issue.

A good alternative was already posted by Newlife.
It was designed for this purpose. It has enough travel that it will not be damaged by the hood and makes adjustment pretty simple.
It too is an NC switch. They are available in both single pole grounding, and single-pole contact (isolated from the mount).

Either that, or a mercury switch. Anything else is mickey-mousing something that was not intended for the application.

The tube is actually pretty durable. You aren't going to break it without a pretty hard direct impact.

 

They are also not bouncing down a road at 60 miles per hour in an engine bay that can easily exceed 200 f.

Now there's a litmus test for safety.

Probably right, until a cop sees flashing lights under your hood at night and want's to know what's up. Not that you'll get a ticket, but is it worth it? Do you really want random flashes of light, from your engine bay, while driving at night?

All I can say is ... wow ...

 

As long as they aren't red or blue, a cop isn't going to care.

And it's not going to happen on a normal road where a cop if likely to see unless you're hitting driveways or speed bumps like a moron. It's going to have to be a pretty extreme hit to make contact.

 

go to a junkyard & grab one plus the wiring harness really cheap. they have been around for a long time on a lot of vehicles. Looked at the one on my 2002 Suburban recently - light& mercury switch all in one. May grab one & put it on my truck. simple install.

 

Did a little more searching and found something very similar to what Newlife posted. Looks like there is plenty of room for adjustments to be made.
http://m.ebay.com/itm?itemId=121270170548&roken=3YmUUe

 

That'll work.
It's a grounding switch, so the fused hot will need to go to the light's positive, and the ground from the light goes to the switch.

Protect the wiring well from chaffing, especially near the hood hinge.