Injected1

Ok I'm hoping someone here can explain how the headlight system on these things works. I'm wanting to buy or build my own wiring harness to provide my headlights with AT LEAST a constant 12 volt current, preferably 12.5 - 13.9v. This is like a future project of mine that I plan on doing when I do an H4 conversion, but I'm trying to get all the info together ahead of time. First off, can someone tell me if it's a switched power or switched ground? I don't really want to mess with the wiring INSIDE the cab, just the stuff under the hood. If I can't find one to buy, I'll have to know this to figure out where to go from here.

Injected1

From what I can tell so far it's a switched ground system using 2 ten amp fuses in the fuse box under the hood to feed a common power wire to the headlights. If I pull the left headlight fuse, the left one gets dim but doesn't go out. Same for the right. It's like it just cuts voltage to it. That seems kinda fishy to me. I thought about cutting this fuse power source and it's associated grounds, putting the power wire into TWO relays as the switched power source, running the ground from the "dim relay" to the ground wire for dim on the cab switch, and running the ground from the "bright relay" to the ground that goes to bright on the switch.

This should in theory ground the "dim relay" when the cab switch is turned on and in the DIM position and ground the "bright relay" when the cab switch is moved to bright. Wouldn't this cause the relay to close a circuit from the battery to chassis grounded headlights. This system would allow me to run larger gauge wire from the battery to the relays (fused of course) and from the relays to each headlight. The current system would just be used to operate the relays. Any ideas as to whether this would or wouldn't work. Or any better ideas for that matter? LOL

mt_goat

I installed this and it works great.http://www.4crawler.com/4x4/CheapTri...#WiringHarness

4Crawler

iTrader: (3)

Switched ground:
- http://www.4crawler.com/4x4/CheapTri...l#HarnessTypes

this is the schematic of the circuit I use on my harnesses:

Injected1

In the COM___LOW___HI factory plug is the COM a common ground or common 12v power? Also, what is port 87a? LO and HI on the factory plug go back to grounds through the headlight switch in the cab right?

I think I got the headlight part. It looks like it flows from 12v source > port 30 > closed to port 87 > yellow or blue line > headlight > common ground.

4Crawler

iTrader: (3)

All detailed on the web page. COMmon power and switched ground via LOW and HIgh beam contacts. 87a is the secondary 87 contact, supplies power to feed back to the high beam indicator on the dash, again as noted on the web page.

Injected1

Oh ok.. Yeah, I've been looking at the webpage.. You have some good stuff on there. I knew that it fed power to the indicator, but I wasn't sure how it got back to the indicator from the relay. I'm still not completely sure how it all that part works yet, but I'm trying to figure it out. I'm at work so I can't look at my truck, I'm just trying to go from my memory.

Injected1

I guess what I was asking is which wire feeds power back to the indicator? You said it just uses an existing wire. Is it the low beam ground wire??

4Crawler

iTrader: (3)

Again, it is all on the page, here is the factory wiring diagram:


And yes, it is the low beam wire and low beam filament that feeds power to the indicator. I guess Toyota saved one switch contact and one wire by doing so, sort of a kludge and is not really a "high beam on" indicator so much as a "low beams not on" indicator.

mt_goat

No need to reinvent the wheel, Roger's kit is good quality and cheap. Just buy, install and go.