Sorry to bump, but I am stumped. I feel like I've gone through most of the steps detailed but seem to be having an issue different from everyone else?
Low beams work fine
High beam Flash works fine
High beams - no light, - 12V going into all three terminals.

I cleaned all the contacts, and checked spacing between them.
I followed the wiring diagram that Rad4Runner posted, power is correct on all wires except R-Y when high beams are on. According to the diagram I should have essentially ground when high beams are on, instead I have close to 12V
As all three wires have 12V when high beams are on I seem to be loosing my ground.

Any ideas as to why this might be happening?

Thank You!

88 4Runner, stock wiring harness.

 

Bump is good.
Correct. Contact should connect R-Y to ground. Focus on that side. Inspect switch for bent pins.
POOR DESIGN OF THE HEADLIGHT CIRCUIT reduce life of the contacts.

 

Low Beams

High Beams
I believe they look correct? Or is the High beam supposed to look different?

Thanks!

 

I'm on smartphone and don't remember which of those contacts are what pins. However, here's how it should work (after bad bend on contact is fixed). Pls note that picture shows defective switch.. Just look at notes below...

 

Blinkers stop working when the headlights are on. Parking lights won't work. Bulbs are good. Getting juice to the bulbs. Light switch maybe?

 

Because you did this? J/K

Seriously,
Blinkers not connected to headlights, but could happen if you have problem with wiring.
Dont know if ur tail light switch is on same stalk as headlight.
If u cud share FJ40 schematic, wud be happy to analyze for u.

 

I know this is an older thread, but here is some information that was helpful to me. Before you pull off your steering wheel and take apart your headlight switch, you can do a continuity test on the harness under the steering wheel stock.

 

So to bump this again. I installed LED headlights with the conversion harness. The harness eliminates the drivers side plug on the original toy harness. I ended up with an issue of only hi beams and no other lights working. No blown fuses and such. I can plug in one of the old bulbs into the unused plug (drivers side) and everything starts working like normal again. So to an extent I have resolved the issue. My question is, what would work as a replacement to a bulb to get the correct resistance or connection I would need without using a bulb to do it. This is on A wheeler so having a bulb bouncing around won’t work. I’m not super electrical savvy so simple is better.

 

This thread is primarily for stock circuit. There is a smorgabord of after-market.circuits out there. In order for us to help, need to know:
1) what LED lightsyou got an d documentation
2) how manufacturer recommends it be wired.
3) What harness you got and documentation, AND
4) Do BOTH original bulns work with stock circuit?
5) Do BOTH original bulns work when plugged into the harness?

 

both originals work with stock. And all running lights work with both originals hooked up. I will try the harness tomorrow. It’s a pretty much plug and play setup. I also tried the LEDs to original wiring. No lights in any position.

 

How about Flashing High Beams?
How about original bulbs with the harness?
Your LED bulbs are most likely polarity sensitive. Would not work on stock.
Please find out where each male pin of LED bulb connector goes, Common/ground, High beam "filament", Low beam "filament".

With harness connected but bulbs out, Measure the following voltages:
Voltmeter + probe to batt + and - probe to pin 3 of harness connector: __________volts

Then with voltmeter negative (black) probe on pin3, + probe on pin 1 then 2
PIn1: headlight off: ___________ volts, Low Beam on: _____________ volts, High Beam on: _____________ volts
Pin2: headlight off: ___________ volts, Low Beam on: _____________ volts, High Beam on: _____________ volts

 

A similar issue has been driving me nuts for years. Sometimes the headlight will just go off, sometimes the high beams will not stay on, then suddenly they start working again after a few minutes. If someone knows how to fix this issue, I woiuld gladly hire someone to work on some light issues. So, if your close to Provo, Utah and want to make a few bucks, let me know. "it's good to be back on the forum". Thanks, I'll continue to monitor.

 

Not close to you so can't help that way but this sounds like a loose or corroded connection. I would start at the plugs for headlights in the wiring and work your way back. Most of the time the plug behind the light gets corroded or damaged causing the connection to be unstable.

 

Another possibility, once the plugs for the lights are verified, is the light switch in the steering column. The contacts are right out in the open, just pull the two covers off the steering column. They tend to build up a layer of corrosion on them, which is easy to remove with some Ruby cloth, or very fine grit sandpaper.

Speaking of the plugs, whenever I pull a plug, I always, ALWAYS put a small amount of silicone dielectric grease in it before I plug it back together. It helps prevent corrosion and dirt from getting in and making intermittent problems.

Good luck to ya!
Pat☺

 

Definitely check connections. However, it is most likely because of bad switch contacts. The headlight wiring is flawed and subjects switch contacts to unnecessarily high current.
It would be nice IF you're comfortable enough with a multi-,meter/ The test points I described on original post would help.

Sorry, too far from you...This was the closest I got to you a couple of weeks back

 

I know this is an old thread, but I have run into this issue with a recently purchased 87 4Runner. PO did a number on electrical with a light bar and a winch. (Aftermarket bumper also removed front blinkers)
It already had LED headlights with no H4 harness and no brights. I didn't like the look, so I bought new lights and the H4 harness, thinking that would fix issue and I would wire in blinkers later. (New light have integrated lamps for blinkers if wired in).
After install of harness and light, I still have no brights, no flash, and no Brights indicator on cluster.(hazards do show).
On H4 harness, here is how I measure out. (All taken on Passenger side closest to battery)Positive probe to batt, neg probe to pin 3 = 12V

Neg Probe to Pin 3-
Positive probe to Pin 1
Off=0
LB =11.3
HB=11.3

Positive probe to Pin 2
Off=0
LB=.06
HB=.06

Anybody else have this scenario going on? I can hear relays clicking.
I am not good at electrical, but I was able to get pin reading.
I am trying to determine if I REALLY need to remove steering wheel to get to contacts, but it seems to be something else to me.

Any help appreciated. TIA

 

Bump!

 

Those are wired backwards (pin 3, the common, should go to battery + through the Head fuse and then Headlight Relay, it looks like yours goes to ground). Toyotas use switched ground (pins 1 and 2). But many LED headlamps want a switched power, so pin 3 expects battery ground and 1 and 2 get switched battery +. Perhaps your prior owner rewired the head lights.

Also, your pin 2 (high beams) looks to be disconnected.

 

This was through the new harness. Isn't it the point of the different harness to make all of that switching for you? It is completely possible that PO rewired lights. Do I need to try getting same readings from the original plug the new harness connector plugs into? How could I have low beams and not high beams if they were rewired....don't they use the same wires?

 

Yes. Start with the basics.
https://www.yotatech.com/forums/f116.../#post52379293