[SOLVED] 1998-2000 high beam wire

Solution
If you don't have DRLs then the Red and dark green striped wire goes to your high beams. If you DO have DRLs, then it's the black and yellow striped wire.

Original post
I've been trying to figure out which wire is for my high beams. I stuck the probes for my multimeter into the spots that I assume are going to the black and red striped wire and the yellow and red striped wire. When I turn on my low beams it reads 11 something volts. When I switch on the high beams it reads the same number but negative. I'm not very skilled with wiring and stuff, so any insight is appreciated. I included some (not very useful) pics below.

 

Put your 12v meter "black wire probe" on the center connector, this the (negative terminal).Turn on headlight to "Low beam", with the "Red wire probe" touch eighter left or right pin. If it read with some voltage, this is your "low", the opposite pin should be "High beam".. good luck..

 

What are you trying to do? (i.e. why are you looking for the hi-beam wire?)

 

@turbodb I'm trying to wire my light bar into the high beams, so to turn on the light bar I'll need the high beams AND a switch on. This will make it easier to turn off the light bar when a car is coming on a dark road.

I tested the connections @Papajohn and got the following results. I tapped into the middle wire and connected it to the switch because another test lead me to believe that it was the high beam wire. Now the light bar turns on with the switch and the low beams OR high beams. I added some pictures of my results below. I'm not exactly sure which wire activates the high beams only.

Low beams on

High beams on


Low beams on

High beams on

 

Gotcha. I was wondering if that's what you were up to. I did the same thing with my Hella lights mounted to the bumper. You can check it out here:

Hella Hi-Beams

And, you want the B-Y wire (assuming same coloring as on my 2000) as shown in my post/wiring diagram/photos.

​

 

Do you happen to have DRLs on your truck? Apparently there's different wiring and separate fuses for high/low beams on those, but my truck just has 1 fuse per headlight.

 

It looks like the R-G wire is going to my high beams. I love how the wires are red/dark green, red/dark blue, and red/black. I'll post an update once I tap into it.

 

Ahh, gotcha. I do have DRLs (now disabled).

Looking at the wiring diagram for your non-DRL situation, it's ground switched, but the diagram is confusing. the switch shows R-Y as being HIGH in the C14 Combination Switch, but the R-G wire seems to to go to the HIGH indicator on the dash.

 

Yeah, the diagram is pretty confusing. I tapped into the R-G wire and it worked! Thank you for your help, I'm sure the information you provided will be even more helpful to people with DRLs lol.

 

Everything works as it should There are two things you need to know, and everything will be clear as a mud

1. Tacoma headlights are ground switching meaning the common for the bulb is powered by 12V as soon ad either high or low beam are turned on and other two contacts will get connected to the ground depending on the headlight switch position.

2. The common is contact number 3 as pictured below. It is not the center one.



The center contact is actually contact number 1 and it is the end of low beam filament meaning it is connected to ground when low beams are on.




The other contact as you can guess is the end of high beam filament. It is marked as number 2.



It is hanging open when the headlight switch is in low beam position. So because when at least one headlight bulb is connected (left or right) it would read the same voltage as common. So in your first test when low beam was on you measured 12 V (or so) between this contact and low beam contact (number 1), because low beam contact was grounded by the light switch.

Now when you turn high beam on (your second test) the voltage will read opposite because now the high beam contact is grounded and low beam contact is hanging open (meaning connected to the 12V common via low beam filament in the other headlight bulb). Makes sense now?

Now your third test - low beams on and you measure the voltage between common (number 3) that is powered from the battery and low beam contact (number 1) grounded by the switch. And you measure 12V. Good thing.

And the last test, when you turn high beam on, meaning the high beam contact (number 2) is grounded via the switch, and low beam contact is hanging open only connected to the common via the high beam filament of the other headlight bulb, so the meter shows zero Volts.

OK, it is not exactly 12 or zero because of the voltage trop on wires and contacts but I think you get my point.


And for your enjoyment here is the diagram (I assume you have US truck with no DRL functionality):




Now the bad news: because the Tacoma headlight is ground switching (the switch is between the bulb and the ground, so the normal way of tapping into the switch with your light bar will not work. It is doable but more tricky.

 

Just tap the 12v high beam signal wire off the stalk. It's only signal voltage to trigger a relay anyway, and the added benefit is you can wire it so there's only 1 wire going through the firewall to trigger the relay that then supplies juice to your lightbar. All your manual switch has to do now is break that 1 trigger wire connection. All your dash wiring ends up being short and tidy.

 

check diagram