Understanding the Hood Latch and its Wiring

I am wanting to add lighting to the underside of my hood for maintenance and general convenience when the sun goes down. Don’t need it all the time but it sure is nice to have when you need it. I like to do things automated if I can, meaning hood goes up, light goes on. The factory hood latch appears to be the perfect way to do that, assuming I can figure out the wiring.

the hood latch switch has two wires going to it, a purple and a white/black. I tested both wires and both have continuity to ground. When I operate the switch to simulate hood open or closed, I am still getting continuity between the two wires and ground.

the truck knows the difference between the switch being pressed or not but I can’t figure out what electrical difference between the two wires. As far as I can tell both are telling me they are ground no matter what.

does anyone know how this thing is wired and how it works? I don’t want to use a ball switch or spring loaded switch either. The ball-tilt ones are way too finicky and the spring loaded ones never hold up long term.

any suggestions for the factory latch appreciated.

 

Hood latch wiring schematic.

 

Thank you!! That is super helpful. Looks like I need to splice into the violet. I’m guessing I was testing ground on it because it ties to the Body ECU which probably has continuity to ground but isn’t actually a ground circuit like my tester led me to believe. I will experiment soon and will also use a diode on the violet wire to prevent my lights back feeding the Body ECU anything they shouldn't.

Just curious, where did you get that diagram?

Thanks again!

 

Got it off this site.
https://www.tacomaworld.com/threads/3rd-gen-tacoma-service-manual-huge-pdf.707834/

 

If I were going to do it, I'd just use a pin switch and keep the under hood light wiring independent of other circuits. This forum is full of horror stories caused by circuit tapping. Plus if an electrical gremlin ever comes up, Toyota can't blame that as the culprit.

 

I have a factory underhood light in my 2000 Ford Ranger. It has a simple mercury switch built into the light itself, so it comes on automatically when the hood is open. (The mercury switch is activated when the hood reaches a certain angle above the horizontal.) Only one wire is needed to supply voltage to the light (the ground is completed through the sheet metal of the hood, but you could also ground the hood to make sure).

You might want to consider this approach with your Tacoma. You could run the wire directly to the battery -- that way, you could have a light available regardless of the ignition switch. (Put an inline fuse on the wire.) This is simplicity itself.

 

My problem with pin switches is that they don’t work for long in my experience. I used one on my frontier hood light and within about a month in the winter, the light was no longer turning on when I’d lift the hood. I’d have to manually grab the switch and pull it up a tiny bit more. Kind of defeats the purpose. That was also a ‘good’ zinc plated one that was supposed to eliminate problems like that.

in general I agree the less splicing the better but for a simple hood ground circuit I don’t really see how much bad could come from it. I do a very good job on splicing that keeps my taps completely sealed. I would install a diode so the computer doesn’t even know anything is there.

Also in consideration if I can find the right oem plugs is making myself a jumper harness to plug in between the hood latch plugs to tap in that way. But I haven’t found the right plugs yet. Actually I have, but only at one really expensive site for $80 for just the male.

 

I had a mercury switch on my 94 Jeep. Worked well enough. However I have never found a mercury switch sold in modern day. Seems like mercury was pretty much abandoned in lieu of tilt ball switches which I don’t like. I tried to find mercury switches I could use on my Jeep or Frontier and found nothing. I’m all for simple, but I haven’t found a way to make it simple yet. It’s going to get wired to the battery or a fuse panel I add regardless, the ground is the one in question because that’s how I’ll control it. I just don’t like feeling for manual switches in the dark and having to remember to turn them off when I close the hood so I definitely don’t want a manual switch as my way of doing it.

 

Call me impractical, but...

 

A toggle switch in cab, or a waterproof one underhood would keep things simple and negate harness tampering.

Plus it means you only have light when needed, not on during daylight when the hood is open.

 

You might be able to find one among the older vehicles at a junkyard.

 

^This. I used one Friday night to change the battery in the 'Frunk' of my GF's Porsche.

Or an external battery-powered light which can be moved to wherever you happen to be working.

My F-550 has an underhood light stock, though it must use some sort of Mercury-type switch as it turns on as the hood is opened. I disconnected it because I park it on an angle next to my garage and noticed that the light was staying on when the truck was parked and the hood was closed.