96 taco only high beams no low beam

low beams suddenly turned off one night and only high beams work.

bought a two new all inclusive headlights and no difference replaced all fuses
Put power probe on headlight plug and got 12.5v for all three
dashboard light indicator comes on with low beam actuation and highbeam
relay clicks as i turn on low beams as well

stumped any help is greatly appreciated

 

Welcome aboard Jared

 

thanks

 

This looks like a question for @RysiuM

 

My understanding is that Dimmer Switch supplies ground for the High and Low beams.
Sounds as if the Low Beam ground is not being supplied?
Then again, I could be wrong.
Maybe someone with a REAL diagram can help you out.

 

@Jmd4993 did not say if he has DRL (Canadian) truck or not, so I assume it is not. For non-DRL truck the diagram with highlighter path (in blue) for low beam (from the bulb to the ground).



Basically when low beam it turned on the blue path should show zero volt and therefore the high beam indicator bulb will be off. The only way the high beam indicator bulb will stay on is if head relay is powered, at least one headlight has working low beam filament AND the dimmer switch does not short "blue line" to the ground. I can eliminate the switch ground issue as if there is a ground problem then the high beam would not work nor the headlight relay would not energize (the the high beam indicator bulb would not turn on). My bet the broken part is a dimmer switch, particularly the wire connector 17 (where the read/green wire is going into the switch). It is quite common issue with older trucks (It is Toyota design flaw imho) because that wire is under constant high current flow when driving at night. Like here: https://www.tacomaworld.com/threads/low-beams-dont-work-high-beams-do.628133/#post-21515244

This is why you should never use high power headlight bulbs (known as "off road" bulbs) without additional harness. And this is one of the reasons I installed LED road legal DRL lights in my truck (DRL or driving with low beam on are required in Poland).

 

Hi all, chiming in a bit late here 1996 3.4L, MT,Xtra cab. I have the exact same symptoms and scenario as the OP though I didn't notice any smoke. Details:

• The problem started the other day when I turned on the cheap supplementary LEDs light I mounted under the rear bumper a while back
• The dimmer switch that likely burned out is a pre-Tacoma one that I installed as part of a LED instrument cluster mod
• I'd like to address the true problem before replacing that dimmer

I figure I also need to replace these rear bumper lights and/or add some sort of harness. Any suggestions? I'm especially interested in hearing from @RysiuM , thanks!

 

May not be related, but I am curious about these supplementary LED lights. How did you connect them?

If this is the sam problem as OP the give away will be 12v on each headlamp contact when switching on high beam.

 

These supplementary lights were just replacements for incandescent ones set up by the previous owner. He wired them through fuses in an auxiliary fuse box that he installed in the engine compartment. I just connected my new LEDs to these same wires.

My high beams work fine on the headlights. I could break out the multimeter if thats useful.

 

And if the blue "hi beam" indication lap is on when low beams is selected I suspect this is the same issue as other had - either the dimmer switch or dimmer switch connector is burned.

That original design is stupid. Only models with DRL (Canada version) have relays to power headlights and the dimmer switch is controlling only low current flow.

This is why I swapped headlight lamp for HELLA lamp taking H4 and used nominal wattage but high quality H4 bulb. And thanks to LED DRL I installed in the bumper insert I burn low beam and hi beam only when driving at night. Even I don't have it in my truck, I recommend installing aftermarket headlight harness even if you are using standard wattage lamps.

 

Yes "hi beam" indication light is on when low beam is selected. After I swap the dimmer switch, how would you recommend I prevent this from occurring again? Swap out head lights?

 

I had an issue with my 96 Tacoma, where the low beams would shut off randomly or when switching to high beams would kill lights completely a lot of random weird electrical problems. Eventually traced it down to pulling out the headlight switch from the column douching the whole thing down in brake cleaner and after drying coating it with dielectric grease and it has been fine ever since.

 

Resurrecting dimmer switch maby possible option, but if headlights were abused by high wattage bulbs ( like 65 and higher) then damages to contacts might be severe beyond repair.

To prolong the life of the switch just use standard bulbs (45/55w) or install headlight harness which power bulbs by its own relays.

 

Thanks, I'll replace my headlights with lower wattage ones to be sure, though I'm not sure what my current headlights are. I also have auxiliary lights: lower wattage LEDs near the bumper and old school incandescent OHV lights on the front. I wonder if the old school lights might be a culprit.

I really don't want to pull apart the dashboard and install or resurrect the dimmer switch only for this to happen again.

 

Hi all, I finally got around to pulling apart the dash and replacing the dimmer switch. No luck :-( I still get high beam indicator in both light positions (high and low beams) and the low beams do not work.

What's my next move?

Note that the "dimmer switches" (the one I replaced and its replacement) are the older electronic dimmers, not the rheostat. I replaced the rheostat upon @RysiuM 's suggestion a few years back (see his post).

[Edit - I tried a new headlight relay, no luck there]

 

I am not sure if you did not confuse "dimmer switch" and "rheostat". I know these are stupid and misleading names but:

Dimmer switch - it is a combination switch (stalk mounted to the steering column) used to turn on headlights and blinkers.
Rheostat - it is a electronic or passive resistance device with a knob mounted on the left side of the dashboard used to changing the intensity of dashboard lights.

For the high beam issue "dimmer switch" (stalk mounted to the steering column) is responsible. Did you replace this one?

 

Ah OK, thanks @RysiuM , yes I did confuse these two things. What I replaced was the knob unit on the side, not the switch on the steering column. Seems like that is my next step.

Mine is a 1996 Taco, so I have the older switch assembly (Toyota 84310-04080). I assume I must replace this entire assembly, am I correct? These is no way to replace just the headlight switch on these early Gen1 Tacos, right?

 

I don't know if you have to replace the entire combo (including wiper switch), I think you can just replace the left side - the "dimmer" switch with turn signal. It is a "monoblok" with all "headlight" wires coming to a single plug. You need to verify if it fits you truck, but I think the switch itself is this part number : 84140-04040 (less than 1/3 of the combo price)

But before replacing the switch examine the plug with wires. It is possible that melted or overheated contacts are the problem, not the switch itself. You may see the "smoking gun" at the contact number 3 (red-green wire) as a possible suspect in the crime. It is cheaper to buy a pigtail with the correct replacement contact (probably less than 20 bucks at Toyota dealer) it is pain in the ass to replace it in the plug, but doable. If the plastic is melted, then a junk yard, ebay or someone parting out may be a possible source.

 

Thanks, yeah I took a very close look at that red-green wire coming into the harness and saw nothing like burns or melting. The dimmer part number is VERY specific to year, looks like mine is 84140-04030. I'll just have to figure out how to pull it out, as I see no YouTube videos for this procedure for my vintage truck.

 

If you have access , disconnect the plug. And check the state of contacts. And while you are there you can easy chcek the continuity between contacts, might save you few bucks.

I have never replaced the switch do I am no help here.