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Electrical / Wiring help for head light low beam switch

11K views 27 replies 5 participants last post by  92JrollaDX 
#1 · (Edited)
I am rewiring my head lights and turn signals and need help diagnosing this switch.

This is the part of the running light/head light switch on the left of the steering column.





I've already rewired my turn signals, that was easy.

Now I'm stuck with the head lights.

Right now, when I turn my head lights on, high beams come on and stay on, unless I press in and hold this button on the switch pictured.

I want to set the low beam switch to a seperate push on/off switch, so I need to know which wires to hijack out of the 4 here.

The switch seems to actuate two separate things though. I'm guessing, telling the blue high beam on my instrument cluster to turn off and with a further press in, to switch to low beams.

What do you guys think?
 
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#2 ·
I haven't seen anyone else take the switch apart, so you may be on your own here unless you search and find someone else that did something like this. Toyota usually uses a similar design across many models, so maybe someone with another Toyota has done it.

Your best chance of figuring it out is getting a wiring diagram, and as luck would have it there's a 1992 Toyota Corolla Factory repair manual with your name on it for $36 on ebay right now with free shipping. You can't beat that price. They don't come up this cheap often. The Toyota repair manual includes all the wiring diagrams.

And as far as the blue high beam indicator in the cluster goes, the power for that bulb goes through the low beam bulbs when the high beams are on. Go figure, right? It's these types of things that you can't figure out easily without a wiring diagram.

The circuit is also tricky because when you pull the level toward you the high beams flash even with the headlight switch off. The wiring diagram will save you time in figuring this all out.
 
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#19 ·
And as far as the blue high beam indicator in the cluster goes, the power for that bulb goes through the low beam bulbs when the high beams are on. Go figure, right? It's these types of things that you can't figure out easily without a wiring diagram.
I can't for the life of me figure out how the dash high-beam indicator can possibly work off the low-beam circuit.

It's in parallel with the low-beams, and should be lit on low-beams?
Only way to resolve this conundrum is an error in manual and wires are switched at bulb-socket?
 
#6 ·
#8 ·
It broke.

Not to mention I have a completely stripped down steering column, aftermarket steering wheel. I've already relocated the horn and turn signals. I think I'll keep the running lights/headlights switch and wiper switch where they are, but the low beams need a rewire to a different location. I was thinking of setting something up on the floor where the clutch would have been if it was an MT, with a foot switch to switch high/low beam.
 
#9 ·
What broke?

My headlight switch broke, but I was able to fix it. Or you can just grab a junkyard switch. But it sounds like you're set on making these upgrades.
 
#10 · (Edited)
UPDATE:

So, Ive recently picked up a floor mounted switch to actuate the headlights. The switch is fairly simple.



My goal is simply to be able to switch from High to Low beams with my foot, period.

After reviewing the wiring diagrams

http://opc.mr2oc.com/online_parts_ca...CorollaFWD.pdf
http://www.autoshop101.com/forms/ToyEWB.pdf

and experimenting a bit, I keep running into an issue when the lights are off. The relays in the box under the hood click on/off rapidly. This happens when the power feed from the battery, red-white wire, touches either the Low Beam, red-green wire, or the High Beam, red-yellow wire, without going through the combination switch. Somehow this switch, probably with the ground involved, eliminates that. In other words, the floor switch works for the headlights when the headlights are on, but when only the running lights are on, or all of the lights are off, the relays click constantly.

This is where I'm stuck. It should be easy enough to insert this foot switch to either have the Low Beam or the High Beam work off of it, if not both. But I'm stumped. :(

Any thoughts would be appreciated.

Pics below for reference:

Red wire = power ; one of the White wires = ground ; the other White wire = running lights (I think)


This is to switch from lights off, to running lights only, to headlights on. With the foot switch in the mix, the relays go haywire when this switch is off, and when only the running lights are on. When the headlights are switched on the relays do not click rapidly and the foot switch works!



This is what the High and Low Beams pass through, it also had the turn signal switch in it. The button in the middle is what is depressed when the Headlight stalk is pulled back.



The underside/inside of the same switch.







With this switch, if the button is not pressed in, the High Beams and the High Beam Indicator on the Instrument Cluster is illuminated. When the switch is pressed halfway in, the High Beam Indicator goes off, and when fully pressed in, the Low Beams are switched on.
 
#11 ·
It doesn't help that the second wiring diagram is wrong. I couldn't download the first one.

When red-white is grounded to ground wire white-black it "turns on" the headlight relay to allow high current to the headlights. This is what you use red-white for.

Red-yellow and red-green have to be grounded to white-black to turn on high beams and low beams, respectively (along with red-white being grounded).
 
#12 ·
Sounds (literally) like you have latching/feedback problem with relays powering themselves on & off due to outputs of some being inputs to others. You need to draw a schematic of what you actually have in the car. Make sure terminals on switch matches contacts and various positions. Build a state-table of which wires connect to which others at various positions of switches. Then tie it all together with schematic.

The first step is to fix the switch and get it working properly in all-stock configuration. Then insert the high-beam foot-switch after that.
 
#14 ·
Once we know what the actual circuits in the car and know how that it's working properly, we can install high-beam switch.

Right now, the problem may very well be a broken light switch that's not setting the relay states properly.

So two things has to be in order for your project to be successful:

1. Accurate schematic of actual light wiring IN YOUR CAR, not some mythical creature on internet
2. Working stock light switch
 
#15 · (Edited)
Working stock light switch √ check

Everything is back to stock.

Accurate schematic... I can't very well rip all the wires out to diagnose, so I have to trust what I can find. I do have most of the colors involved, I think.
 
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#16 ·
Ok, let's go over the stock operation to verify which wires does what and we can go from there:

1. turn light-stalk switch to position #1 is just driving lights?
2. turn light-stalk switch to position #2 and we get driving-lights + low-beams?
3. pull back light-stalk and we get high-beam momentary?
4. push forward light-stalk and we get high-beam full-time?

If this is accurate, we can then measure for continuity at various wires to build a state-diagram of what you actually have in car. THEN we can modify it to have separate high-beam switch. Might need a diode or two since we'll have two high-beam switches in parallel. And maybe another relay as well.
 
#18 ·
Actually, you've got a SPDT foot-switch, so we won't need an extra relay. We'll need to test it to confirm it operates as SPDT.

The issue you're having is not having an accurate diagram of what's actually in the car. Not having a map makes it very, very difficult to get from S.F. to Sacramento. So, let's work up a diagram based upon what we know and can test, no need to trace any wires. This isn't 1892 damn it, we have instruments: test-lights, voltmeters, oscilloscopes, RF detectors, etc.

First, we need to recognize that ALL wires deals with grounds only. There is no power being supplied by ANY of them. Sure you may measure +12v on red/white wire, but that's because it's connected to relay's solenoid coil which has +12v on other side. That +12v you're measuring is waiting to be connected to ground. The main source of this ground connection is white/black wire.

So....use the white/black wire as ground for following tests to see what happens. Everything done on harness-side connectors, there should be 2 going to light-switch. Use paperclips or little short wires to bridge the terminals on connectors:

1. connect light-green wire to w/b-ground, What happens?
2. connect red/white AND red/green to w/b-ground. What happens?
3. connect red/white AND red/yellow to w/b-ground. What happens?

From this testing data, we can build a state-table of factory light-switch on how it works in various positions. Then derive a diagram of lighting-circuit from that.
 
#20 ·
It splits after the low beam bulb. One path is through the high beam indicator to ground. The second path is through the headlight switch (low beam) to ground.

When the switch is on low beam the path from the split through the switch to ground has zero resistance so (almost) all current takes this path. I guess the circuit relies on the fact that the low beam filaments have some resistance upstream so not enough current goes through the high beam indicator to illuminate it.

For "proof" here is a case on the tacomaworld forum where both low beams burned out and the high beam indicator stopped working also. Toyota wired a lot of models this way. There is also a wiring diagram in that thread.

https://www.tacomaworld.com/threads/high-beams-work-low-beams-dont.486224/

Now, the 7th gen wiring diagram is different, but I'm not sure if the diagram is wrong or Toyota changed the design.
 
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#21 ·
Hmmm, i'm going to have to measure impedance of the low, high, and high-indicator bulbs. Splits don't change supply voltage, current used or voltage drops. Odd... I'll have to calculate voltage drops from before and after each filament. This sounds kinda like the alternator charge-lamp circuit.
 
#22 ·
Imagine 2 bulbs in series connected to 12 volts. Both will light and there will be a voltage drop of 6 volts over each. Now connect a wire from the midpoint to ground (a wire in parallel with the second bulb). Now there is no voltage difference on either side of the second bulb (both sides are grounded), so the second bulb can't be lit. The voltage drop over the first bulb will now be 12 volts and it will light up brighter.
 
#24 ·
UPDATE:

My genius brother, with no experience with electrical wiring or circuitry, took a look at the dilemma for a couple minutes and said, "You need to wire it like this."

This here, this here, this here, disconnect these two and BAM!! It worked perfectly.

Amazing.

I have the stock combo switch wired up with the W/B and R/W. I have the R/G and R/Y disconnected from the combo switch. I have the W/B going into the middle of the new floor switch, the R/Y coming from the 1st output of the floor switch into the R/Y going into the series and the R/G coming from the 2nd output of the floor switch going into the series. Neither of the R/G or the R/Y are connected into the stock combo switch.

With this setup the new switch is able to switch from High to Low beams and all of the other things work right, like the running lights, blue High beam indicator, stalk switch, off, running lights and head lights all work. No feedback loops.

Awesome!

Thanks brother!
 
#25 ·
Good job brother!

So you've got stalk rotary-switch used just for on/off. R/W = headlight relay activation when grounded.

Then the floor-switch used for selecting between low/high. R/G = low-beam or R/Y = high-beam when grounded

What happens when you use momentary flash function when pulling back on the stalk? In stock configuration, this lights up both high and low-beams.
 
#26 · (Edited)
Here's a pic of the switch installed. I'm more concerned with function over form, so looks don't concern me too much.



Interestingly, my brother suggested leaving the stock combo switch out of it entirely, which is what I have done. I do still have the stalk switch to turn the lights off, to running lights, or to headlights. I no longer have the option to flash the lights, but this is something I never used anyway. I left the R/W disconnected from anything. This must give you the ability to flash. The W/B is run to the center of the foot switch and R/Y to one out/in from the floor switch and R/G to the other out/in. That's it folks. Everything works perfect, minus the flashing both lights ability.

Super easy to push and quick, and fun at the same time.
 
#27 ·
R/W is still connected through rotary switch. That's the first-stage that turns on the headlight-relay. When you turn switch to headlight position, it grounds relay which sends power to headlight-bulbs. Your foot-switch then determines if low-beam or high-beam circuit is grounded.

Flash uses same R/W, R/G and R/Y and grounds all three of them to W/B:
- grounds R/W to activate headlight-relay
- grounds R/G to turn on low-beams
- grounds R/Y to turn on high-beams

Flashing doesn't work now because the R/G and R/Y has been disconnected and re-routed to foot-switch.

Did you use as thick of wire to run to foot-switch as original R/G and R/Y wires? No need to extend W/B wire, run short wire from center-terminal of foot-switch to chassis bolt somewhere nearby.
 
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