96 taco only high beams no low beam

Where did you find it? I've been searching myself so I can give better info next time.

 

Ha!

https://www.tacomaworld.com/threads/no-low-beam-headlights.379610/#post-10422490

 

I am 100% sure both filaments will light up when you select high beams. You may not see it and have a great feeling that you lights are twice brighter on high beams, but H4 bulb (or H6054) are not designed to run like that. You will put 115W in each H4 lamp, (or 100W if you have H6054) that is 20A total throug the headlight relay and wiring. That is almost two times more than it was designed for. For that wattage people use a separate headlight harness. In that context shortening the bulb life is just a minor inconvenienc.

There are cars that do not switch low beams bulb when turning on hi beams. 5th gen 4Runner for example, but low beam and high beam are two separate bulbs in two separate housing. And the entire circuit is designed to handle the load.

It's your truck, do as you please, but do not recommend that solution as it is just wrong and can cause an electrical fire.

 

Thank you for your opinion. I can 100% guarantee you are wrong. Nice explanation from a keyboard warrior with nothing better to do than look up bulb numbers that don't matter, the bulb works or it doesn't.
Did you even bother to read the thread that was linked above?
Listen, try to keep up.
There are TWO positive leads to the bulb, ONE negative. When switching from low to high, one positive goes cold, and the negative wire switches with it. That's right, the negative wire attempts to use a different ground path. Prolly has something to do with the indicator light on the dash that also acts up when this problem occurs. That's why you get continuity with the ground on high beams and no continuity with the ground on low beams.
Solution, supply a new ground path. No, both filaments do not light up because of the simple fact that only ONE positive lead is active with either low or high beams.
And you will lose the indicator light on the dash, no big deal.

 

So you are saying that the FSM diagram is completely wrong and backwards, the combination switch is not part of the ground loop, the ground only goes through the indicator for high beams and despite there being only one ground wire somehow the indicator magically knows whether the low beam or the high beam is on and lights accordingly?

FYI, it doesn't matter what headlight bulb number you're talking about, they all have three terminals if they have hi and lo in one bulb. Because that is the case, regardless of which way the current is flowing there will be one of the three wires connected in the middle of the filament and the other two connected to the ends. Some bulbs, like 1157 turn signal bulbs look to have two separate filaments, but when you get down to it it's a Y connection. Therefore, you can have both on.

I'm not saying anybody is wrong, just how you word your explanation makes no sense from an electrical perspective. No idea what Rysium does for a living, but I'm an industrial controls electrician not an armchair warrior. That's why I won't say anyone's wrong until I've had eyes on your wiring. Just saying, coming from an electrical background, what you say doesn't make sense. I don't have a 96 and I have no stake in the game except the curiosity to want solve a problem.

 

I read your thread and if that many people had success with it than I have to conclude that the diagrams are wrong like you said. The power must be going through multifunction switch then to the lights. Ground might be too in order to make the indicator work. That's really disturbing that the diagram is so messed up.

 

And here's a contrary thread:
https://www.tacomaworld.com/threads/solved-1998-2000-high-beam-wire.696687/

 

So is it positive switching or negative switching? The debate goes on

 

The problem is most likely right behind the instrument cluster on the PCB where the dash lights are. The High beam indicator going wonky is the common denominator for when this happens. Now that's just an opinion, not the facts I stated above about the work around, but it's prolly a failed solder joint on the PCB, no longer allowing the redirect of the ground.

Easy enough to check with a cheap multimeter, one headlight plug wire should be hot on low, the other hot on high, and check continuity with the ground on both high and low beam. If you lose continuity to the negative wire, but the positive is still showing voltage, then give it a ground and the lights will turn on.


The positive wires to the bulb are still doing their job, the ground is leaving the chat when switched to low beams.

 

Ok I give up. Looks like all 1st gens are wired the same with maybe the exception of units with DRLs so I guess I can get satisfaction either way when I reassemble my truck and get my fluke out.

 

You are correct: all 1st gen are wired the same way with ground switching. Regardless of the year. With exception of DRL version (aka Canadian version) which is positive switching and uses relays to do the job - the switch itself is low current.

As for my "chair riding" i have master degree in electrical engineering, so I can figure out which way electrons are going. I can read diagrams and follow wires. And I do have my hands very dirty also in electrical wiring in all my cars, as I do not let any mechanic to screw up with my babies.

 

Update: I used the fix documented by @Deathbysnusnu (negative wire connected directly to one of negative headlamp plugs). It worked as described: low beams now work, no high beam indicator light in either low beam or high beam mode. I can live with this for sure. I do wish I could fix this properly and find the actual location/cause of the problem, but after looking/testing, tearing apart my dashboard, disassembling my steering column stuff, buying/installing a new headlight dimmer, etc., I just wanna be done with this, at least for now.

Thank you for your help everyone! Really appreciate it

 

Glad you got it working while we had fun arguing over it. lol

 

EPILOGUE: Shortly after the aforementioned fix (negative wire connected directly to one of negative headlamp plugs), the same headlamp burned out. I verified that this bulb was kaput via a continuity test. I also tested the leads on both of the plugs and I received full voltage on both headlamp plugs. What the heck!?

Anyway, I went ahead and bought some new Hella + H4 headlights/bulbs and installed them and everything works perfectly now without the negative wire fix, even the high beam indicator light. I have no idea what caused all this in the first place, but I ended up with a fix, plus the Hella + H4 upgrade. I'm also seizing this opportunity to replace my front grille with a new one since I'm taking old one off as part of replacing the lights.

Again, thank you to everyone. All's well that ends well...

 

It'll be interesting to see how long your new bulbs last. I guess it depends how much you use your high beams.