Hi all, I have a 1993 4Runner (22RE SR5) that I inherited from my grandpa. It sat for 15 years at my uncle's house before he was willing to let it go. The idea was to do a bit of the restoration work myself, but I'm starting from very little knowledge, so a local shop took care of a few things to get it as far as it's come. Headlights worked fine when we picked it up two years ago, both low beams and high beams, but it's mostly sat in our driveway since then. Recently, I noticed that the high beams work fine for both headlights, but the low beams do not work (but we have side marker lights when switch is set for low beams and for high beams).

Here's what I've tried:
- Replaced headlight relay. (I realized afterwards that since the old relay clicked when the knob was turned for low beams the old relay was fine.)
- Removed dimmer switch from combination switch and filed contacts. This did not solve the issue. (I filed all contacts with an ignition point file.)

Since I don't really know what I'm doing in regards to electrical, it's possible I could have missed something with the dimmer switch, but I'm not sure.

Today I removed the passenger side headlight bulb. See pic below. Visually it looks fine as far as I can tell.

I tested resistance on the bulb with my (cheap) multimeter. At the "200 ohm" setting, the two outer posts had a small resistance number (RG/RY pair in wiring diagram below), but I was only able to get a small resistance number for the other two pairs (center and left, and center and right, RG/RB and RY/RB in wiring diagram below) if I went up to the "20M ohm" setting.

I honestly know virtually nothing about testing electrical and reading wiring diagrams, but would love to learn. I'm not sure how to interpret these results, and if the bulb's high beam filament is bad or if it's ok.

If the bulb is fine, I'm thinking the next step is to figure out how to test the wiring between the bulb and the dimmer switch, and I don't know what resistance range settings I should use in that case, if I want to set it at the lowest setting or if I need a higher setting.

If the bulb is bad, is swapping to LED a good idea on these older trucks, or should I stick with a Toyota bulb?

If someone could help me out here, whether a referral to a good website to learn about electrical wiring diagrams from (Google seems to hate me and I cannot find what I'm looking for) or some guidance about how to continue to diagnose this electrical issue, it would be hugely appreciated. Thank you

 

Update: Thanks to massive burnout from my job, my brain wasn't functioning and I apparently got the color ordering mixed up and switched green and black--big oops. So it’s starting to make sense.

RY/RB has minimal resistance, which I'm guessing corresponds to the high beam filament being OK.

The other two pairs have very high resistance.

RG/RB high resistance probably corresponds to the low beam filament being bad, if I’m interpreting this correctly.

I am not sure why I got that result for RG/RY though since it seems like they shouldn’t be connected.

Anyway, I’ll get a Sylvania bulb at O’Reilly’s tomorrow and put everything back together and see if that fixes it. I was initially thrown off because the bulb filaments looked fine, and I'm used to burned out brake light bulb filaments looking pretty nasty when they quite.

If that doesn't work, then I'll try the troubleshooting advice in the awesome headlights sticky thread in this forum, which I just found (thanks Google for not helping me find that great thread initially...)

Hopefully I can eventually figure out how electrical stuff works.

 

So was an H4 conversion done? I think but could be wrong the 93 had sealed beams stock? Maybe someone else can verify

 

Nope, headlight setup is completely stock. Never been touched since it left the factory I'm pretty sure--my grandpa kept good records and there's no record of anything ever being done with the headlights. He only put 39k miles on it in the 14 years he was driving it, so not much needed to be done when he had it.

 

Ya I just checked from what I see the 91 was sealed and google says 92 has the housing with replaceable bulb, I have a pickup so I had to refresh my 4Runner info I had pickup in my head.

 

Hope a bulb fixes it, I have seen bulbs that look fine that are bad good luck and report back your findings!!

 

Great to know, and yes I will report back once I swap the bulb out and get the battery back in!
Fingers crossed that work won't be too crazy this week and I'll have time to get to it soon.