Hello, and thank you for your help.

A couple of days ago I parked my Scion 06 xB and had a neighbor come to me and say my headlights were on. I go to my headlight switch lever and I see that its actually in the off position. So since it was night I just disconnect both 10a fuses under the hood that control the headlights and they turn off.

Yesterday I start troubleshooting and reconnected both fuses and both headlights remained on even on the Off, taillight, and high beam setting. I got my meter and tested both fuses and showed good. I then went to the headlight relay under the dash and swapped it with radiator fan relay of same type
and no difference. So I ruled out fuses and relay. Is there another relay? I'm looking at the wiring diagram and it shows the door lock control relay located under the speedometer inside dash is connected to the headlight relay. Can this be my problem maybe?

So what I did is order a headlight switch lever the one that goes to the side of the steering wheel thinking I narrowed it down to that. I get the part replace it fast, and headlights suddenly are now off. I thought yes I solved the problem so I turn the lever to headlight low beams and nothing no light. I turn it to high beam and yes high beams work as well as the taillight setting in the middle. Bulbs looked fine but just for the heck of it, I go and buy a new one and plug it in and same exact thing happens no lights. So question is why did a new lever make an opposite effect of going from headlights staying on to headlights not turning on but every other setting working? With the bulb plugged in and back probing all the wires I'm getting 12v on all the wires which I find odd that when I test the bulb connector with bulb unplugged, I get 2 12v and the other no reading like a ground basically.

Please help I'm returning the headlight lever because I think its defective maybe? and my exchange is on its way, but any thoughts?

__________________

 

Sounds like a tricky electrical problem to me. Your multimeter should have a resistance or continuity setting?? That should help determine if the switch is working properly and also if the wires and fuses are OK. Is there a manufacturers name on the headlight switch somewhere? (lets hope it isn't Lucas)
Lights staying on is odd and it does sound like a solenoid / relay is malfunctioning somewhere.
When you pulled the headlight relay, did the lights go off? If not, they are getting power from somewhere else and you will need to inspect the wires to see if mice have been chewing on the wires.

 

Thanks for the reply. When I disconnected the headlight relay located by the left lower kick panel, the lights did not go off but when I disconnected the lever the lights did go off which is what made me buy another lever only for this one to now give me the opposite effect lol. I now can't turn on the headlights but everything else on the lever works. I live in Los Angeles so none of my vehicles have ever had the rat chewing problem but my computer is located under the glove compartment and the wires are exposed a little but not sure if something on the conputer will give me this effect.

Yes my meter has continuity resistance can you walk me through how to test the lever if it's defective or not? Where do I attach leads and what I should be getting etc. Thanks.

 

Thru the switch, there should be no resistance, or it should be very low, so continuity mode works best.

In continuity mode, just touch the 2 probes together and the meter will beep, indicating a complete circuit with no/low resistance.
It saves having to look at the meter, while you are trying to hold the probes on the circuit being tested.
Only use this mode (or resistance mode) on circuits with no power in them, or it will pop the fuse in the meter.

So find the power input to the switch and hold one of the probes there. Check the other switch terminals with the other probe and see which ones beep with the switch in all the various positions.
Make a note of these.
If you have the old switch, compare the 2.

You can now check the connector that attaches to the switch by tracing across the downstream side of the switch (Not the power cable) and see if you get a connection to ground thru each of the other connections. If there is a relay in the circuit you need to pull the relay out,
after this initial check, and see if you can get continuity thru the relay socket. Not sure how the circuit works, but this part will check the connections thru the car harness to the headlights and possibly back to ground. It's complicated and takes patience and a bit of logic, but you can do it.

My daughter had some headlight wires chewed by a rat/mouse on her Corolla (fun to fix) We live in the PHX area. With the Covid shutdown, the rats are out looking for food as they can't get it from the dumpsters anymore and the soy based ink on the wires makes them smell like food.
Mmmm Tasty, until they chew thru the copper wire inside.

__________________

 

Replacement lever just came in this morning and no difference so I know it's not the headlight switch lever not turning my headlights on. High beams and everything else works except the low beams.

I don't know if it's this after market brand but the chances of 2 being bad im sure are very low.

 

Can anybody tell me if at the headlight connector I should have 2 grounds and 1 positive or 2 positives and 1 ground when the headlight switch is set to on for low beams?

And also what it should be when the switch is off? Also the door lock control relay has a red wire shown in the picture I'm providing and is that supposed to be a ground or a positive?

My remote on my keys the unlock and lock stopped working before this problem occurred but not sure if that's related. Thank you.

 

This is where it gets hard for me. The circuit looks odd - don't understand why the door lock relay goes thru the headlight relay. Is that to flash the lights to show lock/unlock???

The bulbs have 2 elements in them and the way the diagram is set up it looks like the power comes in from the top (I can be wrong here), goes thru the bulbs and then the combination switch connects either the high or low to ground or turns them off.
My guess is there is something wrong with the B-W wires between 7 (1M) and the junction connector; the junction connector itself or the wire from the JC to the Combination switch.
The B-W wire seems to be the low beam - can you get connectivity from the B-W wire at the headlight bulb to any of the other connection points
OR
Can you take a wire and connect the points 7 (1M), or B (A) 2 places to ground and turn the low beams on??

That other headlight relay on the left is suspect too if your doorlock isn't working right.

Sorry, that's the best I have

 

Wanted to update my post with the solution I found.

The problem was defective aftermarket parts as I had bought a brand new headlight switch lever and my headlights turned off from being constantly on but stayed off.

I then returned it for an exchange and same problem existed. So i canceled the headlight switch lever as my problem since no way 2 new switches would be bad I thought.

So I went to my local junk yard and picked up a door control relay as the diagram led me to this part and while I was there I said why not ill get another switch but this time OEM and used.

When I got home I quickly connected the used headlight switch and to my surprise headlights now turn on and off and everything is back to normal. Very rare problem I know but I really believed it was the switch all along and I'm glad its all over.

Thanks to everyone for their help.

__________________

 

Thanks for the update.
im having the same issue (stay on). Now I know where to start.

 

Much, much faster troubleshooting technique is to measure power starting from battery +12v terminal and trace it to headlights. Test every junction on circuit schematic and it should be either 0v or +12v depending upon state of switch. Where your measurement strays from what it should be, shows problem between that point and previous test point. Can find this problem in 5-minutes or less without wasting time and money buying brand-new perfectly-working parts to replace perfectly working parts on car and nothing changes.

Basically you want to measure, test and positively identify what problem is. Then replace or repair just that part and problem is fixed in single pass. That's how professional mechanics do it at dealers. They follow procedure in manual or use logical thinking since they don't have tonnes of time to waste or an entire warehouse of every single part possible for every single car to swap and guess at problem.

Oh yeah, always buy OEM parts!!! Aftermarket parts are so bad, many of them are bad right out of box. If you must buy them, be sure to TEST them before installing to verify they are indeed good.

 

Here's simple way to troubleshoot this even without multimeter. Just look at circuit diagram!!! Note that power goes to headlights FULLTIME. Then two situations turn ON headlights by providing ground for circuit. Either door-lock relay provides ground, OR headlight-switch. Let's look at 1st scenarios:



Note that door-lock relay activates headlight relay and connects ground side of circuit and turns ON headlights. When door-lock relay releases head-light relay, path to ground is disconnected and headlights turn OFF.

Here's what happens when you turn ON headlight switch:



Again, full-time power is ON to headlights. Then it flows through bulbs, then headlight wires, then through OR circuit of junction-connector and arrives at headlight-switch and stops. When headlight switch is turned to low ON position, this provides path to ground for flow and headlights turn ON.

So... if your headlights are ON all the time, what's an obvious test? Test if headlight-switch breaks circuit in OFF position!!! Disconnect headlight-switch connector from harness and see if headlights turn OFF. If they do, then you know something's wrong with headlight switch because it's supposed to disconnect circuit in OFF position. Second confirmation test is to measure continuity/resistance between terminals #8 and #11 of headlight switch.

OFF position = no-continuity/infinite-resistance/open-circuit
ON position = continuity/zero-resistance/closed-circuit

After performing this 2nd test with multimeter, you'll find these results:

OFF position = continuity/zero-resistance/closed-circuit
ON position = continuity/zero-resistance/closed-circuit

Headlight-switch doesn't disconnect headlight circuit when turned to OFF position! That's why headlights stay on! Simple 5-minutes of troubleshooting, no money & time wasted running to auto-parts stores or junkyards to randomly shotgun pile of parts at car wishing/hoping one of those is problem. Note that door-lock and headlight-relay are not used in normal operation of headlights in anyway! Only for flashing headlights when unlocking & locking doors.

It's headlight-switch that transmits ALL power for headlights. That's why switch fails, especially if you install higher-wattage than stock bulbs. All that current going through headlight-switch melts/welds the metal contacts together and doesn't release when you turn switch to off.

 

wow ... that's a tough one...
Glad you got it fixed ...
Do you remember the brand of the aftermarket switch ... I'll stay the hell away from them ..................

I have similar issue with daughters 2006 xA
No low-beam on either side hi-beams other functions are fine.

Raining here today but have printed out @DannoXYZ schematic and will dive into this tomorrow I hope!



Thanks!
Jim

 

No low-beams might be caused by switch not making contact for low-beam position.

1. Measure for continuity/contact between #8 & 11 terminals of switch connector when turned to low-beam ON position. If no contact, switch is bad.
2. Can also verify by bridging #8 & 11 terminals on harness-side of connector. Lights should turn ON.

If not, we'll have to troubleshoot further upstream...

 

Thanks @DannoXYZ will hope for decent weather tomorrow.

The shop manual implies that I have to pull the steering wheel to remove the trim bezel to then replace the switch?
@scion24 did you end up having to pull the steering wheel?

I have a puller but ... like to NOT use it ...

 

Sorry not to post back with the results.
I went ahead and ordered a new unit before tackling the job and it was a good thing I did.

If anyone else is wondering YES, pulling the steering wheel does seem to be required.

In my case the problem was caused by the dealer-installed keyless entry option when the car was new...
It was one of the crappiest wiring jobs I've ever seen and over time the main headlight wire shorted out ... burning thru the switch assby.

I fixed up the wiring, installed new switch, and... all is good

Thanks for the help! Esp. @DannoXYZ for the schematics!

Jim

____