Low Beam Headlight Issue, Only Brights Work

I first noticed this issue about 10 months ago. I went to start my 03 Tacoma and when I started it, I noticed the brights indicator on the dash was on. The strange thing was that my brights weren’t on, and neither where my low beams. The headlight switch was in the “on” position, but instead of the low beams working, I just had all the other parking lights, as well as the brights indicator on the dash.

I replaced the turn signal and headlight switch assembly and when installing the new one I noticed that the wiring harness that the headlight and turn signal assembly plugs into was burnt on the left side. After a good cleaning and installing the new switch assembly the problem went away....

Fast forward to now, I’ve had the same issue. No low beams, and the brights indicator is on when my normal headlights should be. I cleaned the wiring harness again, of which I’ve posted a picture of what it looks like. I can’t seem to fix the problem even after cleaning the contacts. Do I buy another headlight switch assembly? I’m looking to fix this problem as I can’t continue to drive with my brights on 24/7...

Any help or advice would be appreciated!

Thanks

 

looks like your going to need a new plug and terminal.

 

New plugs also follow the circuit, something is shooting out to generate the heat. Broken wires near tilt joint is where i usually find wire issues.

 

Something is crossing between the low beam and high beam. That much heat to melt = very high amps getting pulled. You will have to trace the low and high beam wires from the front all the way back. Then from the fuse box back into the cab. If it is able to melt connectors and crossing high with low beams, sounds to me that the problem is before your fuse box.

Wish i could take a look at it. So much easier to diagnose electrical issues. Also, get you a meter and see what kind of resistance you're getting and what you can do as well (truck off) is hook one side of the meter to power on the low beam and the other to the high beam power wires and see if you have continuity. If you do, your wires are crossing. Sounds like a fun challenge lol

 

I like calling these issues vampire grounds. Happens alot up hear hot wire arcing to a ground causing mysterious issues, all rights flashing or going on. Usually find them with blinker circuit though.

 

Well that looks like the connector for the headlight combination switch. Connector # C14 part number 90980-11672.

And it looks like contact #17 is burnt. Contact #17 is the combination switch enabled ground for the low headlight circuit.

FYI. Once a contact is chared like that, no cleaning can fix it. The connector and the #17 pin needs to be replaced & soldered in.

If this were me trying to diagnose this. I'd replace the headlight combination switch if it appears at-all scorched or burned. Replace the C14 connector and cut out pin #17 and solder in and shrink wrap a replacement in.

THEN! Start to figure out what's caused this.

Inspect and clean all the headlight connectors w/ elec contact cleaner, since an internal short within the HL bulb is difficult to view I'd replace the headlights. Clean and inspect the two ground points for the headlight circuit. They're located under the kicker panels on both LH and RH sides of the cab (near where the doors meet/hinge on the inner rear of the fender).
And if you want to be 100% sure you've gone through everything.. They're two junction connectors under the engine fuse block, that can be inspected. And then lastly on the back of the body ecu there are two connectors that should be disconnected and inspected. 1K which is located second row from the top in the middle and the connector directly below 1K , which is connector 1J.

Good luck.

 

Hey!! I have a match to your burnt plug with exact symptoms, I “cheaped” out and purchased a second hand switch which had the same melted plug! I then purchased a aftermarket switch which has worked for about a year and is now showing the highlight indicator off and on, does anyone have experience with this as it seems common enough?? Lmk mahalos!

 

Unfortunately this is the result of shitty (cheap) design that pushes current from both headlights through that one small contact. That is 10Amp . Once the contact gets a little resistance (from heat and age) it goes downhill very fast (resistance => more heat => more resistance => more heat => burned contact).

Like @License2Ill wrote, once it starts heating up no cleaning will help. Replace contact, connector and if matching connector is discolored it has to be replaced too.

Nobody wrote it here and it may not be a case, but just to be sure do not use oversized bulbs (of wattage higher than 55/60 W). 80W or 100W bulbs without dedicated harness will kill the stock wires/contacts/switches and may even start a fire to Tacoma.

 

Sounds legit! I was hoping someone had firsthand experience since it would seem fairly common, but I’ll take it, check connector opposite the switch and replace as needed, great call on light amperage as well, thanks!

 

Yes, a 4 year old thread but didn't want to start a new one with the same subject. Anyway, I had this happen to my 2002. I cleaned the connector and purchased a new switch. Worked for a while so I thought I had fixed the issue. Well, months later on an extended period 30 minutes on backroads with the high beams on it started happening again. I flicked the high beams off and no headlights at all.

At this point I realized I need to swap the connector out and re-pin pin 17. However, is there anything permanent to keep this from happening again. I've searched quite a bit but I don't see any permanent fixes...perhaps there's not one other than just dealing with it.

If anyone does have any permanent fix (alternate wiring, better connector, ect..) please let me know. Thanks!!

 

I did some more research today and found this thread:
https://www.tacomaworld.com/threads/the-ultimate-headlight-upgrade-h4-not-led-or-hid.398066/

I wonder if this will bypass the factory headlight wiring to allow me to regain function of my high beams and allow me a chance to upgrade the bulbs at the same time. Thinking of going with the Headlight Services Harness as suggested by crashnburn80 on this forum.

I assume the headlight switch will function as normal but when it comes time to put the juice to the headlights that when the new harness will carry the electrical load and not cook pin 17 again (see post 10).

Thoughts?

 

I think what crashnburn80 did should have been done in factory by Toyota in the first place. Running high current directly through switches is very old school and should be forbidden since relays were invented. What is curious, a Canadian version (factory DRL) switches headlights by relays only (only low current runs though switches). Why they did not do it for all versions puzzles me for all these years.
By the way crashnburn80 is one of the most knowledgeable people on this forum regarding vehicle lighting. He knows his things.

 

Thanks for responding and the insight to this issue as well. That’s very interesting about the Canadian variants. It’s not a good feeling to be going down the road with your highbeams on, flip them off, and then have no lights at all.

funny thing is I’m going through the same thing with a 1971 Satellite. Chrysler designed everything to run through the headlight switch. Only problem was as the wiring got older and higher powered halogen replaced the older lower amperage factory lights it ended up putting too much of a load on the factory wiring. When I pulled my old harness out, one of the pins on the headlight switch was super toasty. I’m actually having someone on the Mopar community build me a head headlight harness utilizing relays.

I just ordered the connector that goes to the headlight switch from Toyota today. I think my game plan is to replace that connector, purchase the Headlight Service harness, and hopefully call it good. Although pricey I may spring for some OEM headlight lenses as mine has seen many miles (387k).

 

Interesting ^^^^
The 71…..12v or 6V?

 

12v. I ordered all new M&H wiring harnesses from Year One (dash, headlight, engine, wiper, and heater box harnesses). Started reading on the B body Mopar forums and started learning from the electrical gurus similar to crashnburn80 in this forum.

i’m also having that guy, in addition to the headlight harness, build me the bypass cable that will bypass the factory bulkhead connectors (Packard connectors)because they are prone to corrode and generate heat especially if you put things on it like electrical fans, EFI, ect…. Or run a higher amp alternator than factory specs.

Funny (not really) I’m having similar issues on two vehicles. However it appears in both cases a related headlight harness will solve both.

 

Pm sent