Headlight electrical issue

[TEXAS 57]

Hi all,

I have searched and don't see anything resembling my issue.
1999 LX470
Recent purchase (one week ago)
Headlights worked fine for a couple days (on/off/auto/brights/floods). Now the lights don't turn off after turning the vehicle off.

Here are the issues:
Turn lights on manually - the brights automatically come on. I cannot turn the brights off at all. I can hear the dimmer switch working.
After lights are on - I cannot turn the lights off until I disconnect the battery. Reconnect the battery and lights are off until I turn them on again.

Obviously, this is getting old after two days. I pulled the dimmer relay so I am not driving with brights on.

Any ideas or similar experiences?

 

[kruisinkid]

Without looking at the EWD i would say one of the headlight relays is corroded to the point of being stuck on. Do you have aftermarket bulbs or led’s or an aftermarket harness with relays that could be broken or corroded?

 

[TEXAS 57]

Nothing aftermarket, it is all stock. I was thinking a relay could be getting stuck on and not resetting to open position with the switch but then when the battery is disconnected, it interrupts the circuit. What do ya think?

 

[kruisinkid]

The lights come right back on when the battery is reconnected right? Relays dont reset so to speak but the coils de-energize. In the most simple terms, a relay coil is being energized by the switch from the headlight stalk and power from the headlight fuse is then allowed to flow to the headlight bulbs. The contact from the fuse to bulbs is probably stuck closed

 

[kruisinkid]

The headlight electrical system is much more complex than that example but i would start with pulling headlight fuses and then start pulling headlight relays

 

[TEXAS 57]

Well, I have pulled and reinstalled all the fuses and relays associated with the headlight system. That didn’t work.

I also switched the headlight and dimmer relays with the known good ones from my 2002 Land Cruiser and that didn’t work either.

My next guess would be the actual headlight switch on the stalk.

Any other ideas?

 

[kruisinkid]

Im looking at my 2000 LC EWD. Yours maybe different. The 10A head fuse(rh-lwr) powers the coils for the DRL relay no. 3. Does pulling just that fuse kill the headlights and reset the system? What happens when you engage the parking brake? Thats supposed to kill the DRL lights. That signal goes to the main DRL relay. I cant imagine its a switch as it can be reset with a power cycle upstream. After those 2 tests its time to start metering around

 

[TEXAS 57]

Pulling the HEAD fuse will turn the lights off and resets the sytem. Pulling the parking brake has no effect on anything.
I DO hear the click in the DRL Relay on the Pass side near the headlights when a disconnect the battery or pull the Head Relay when the lights go off...

 

[kruisinkid]

The EWD doesnt show what is going on in the MAIN DRL relay. That makes me think its probably a small box with a PCB inside which is the most likely to fail if you really isolated the other 2 or 3 DRL relays and put in known good ones. Cycling power causing a reset sounds more like a bad capacitor or transistor or IC. I dont have the book in front of me but if its not hard to pull out i would try inspecting that MAIN DRL relay.

 

[kruisinkid]

Re reading your previous posts it doesnt sound like you swapped any of the DRL system relays. You just proved that pulling that fuse kills the coils of the NO. 3 drl relay so i would think its something to do with one of the drl relays

 

[TEXAS 57]

So doing some more diagnostics, I think you are correct. The main DRL may be the culprit.
I have switched the HEAD, DIMMER, and DRL D2 / D3 relay for known good ones.

So things have changed a bit:

DRLs work fine.
Parking lights turn on and off
Headlights / taillights turn on manually or on auto but when I switch back to parking or off the brights come on.


Now I need to get to it...

 

[TEXAS 57]

This morning I switched out the main DRL relay with a known working one from my 2002 LC.
Nothing.
Every symptom is the same.

To recap:
I have switched every relay out with a working one and nothing has changed.

The only other item I see in headlight system in the EWD is the Instrument ECU (I19).

 

[kruisinkid]

dang! so to make sure, here is a list of all the changeable parts inline with the headlight system

-HEAD relay
-DIMMER relay
-DRL relay MAIN
-DRL relay NO. 3
-DRL relay NO. 4 (some model/year variants, possibly LX and 2004+)
-15A ECU-B Fuse
-15A GAUGE fuse
-10A HEAD (LH-LWR) fuse
-10A HEAD (RH-LWR) fuse
-20A HEAD (LH-UPR) fuse
-20A HEAD (RH-UPR) fuse
-parking brake sensor
-auto light control sensor
-theft deterrent ECU
-combination switch at steering wheel (which includes the "Dimmer switch", "fog" switch, and "light control" switch

i think thats about it. i would just make sure you pulled every fuse one at a time and record which ones have an effect on the problem, replicate the problem, pull a fuse, wash rinse repeat. next would be relays, and then i would start metering around and figure out how far upstream the issue is. having the correct EWD for your year and model is invaluable. i dont think guys realize how much the electrical systems changes almost year to year and certainly different enough from LC to Lexus. and check corrosion on all of the associated connectors and junction blocks.

 

[PabloCruise]

Resolution: Electrical Woes - need direction - https://forum.ih8mud.com/threads/electrical-woes-need-direction.1118700/#post-12208877

 

[LXfromTX]

Hate to resurrect such an old thread but I'm having similar issues on my 99. The question I have is:
Can you remove the dimmer relay from the top without pulling the whole fuse/relay panel apart from the base? I looks like they (relays) should be removable if you open the little locking tabs but my dimmer relay doesn't seem to want to lift out. I thought I had read previously that the relays in the box by the battery were not replaceable. The troubleshooting above leads me to believe that they are removable from the top without opening up/splitting the whole box - at least on a '99 LX.

 

[LXfromTX]

OK, more tugging and I can confirm that you can remove the relays individually.
Next question: The EWD does not show how the high beam bulbs run a lower voltage in DRL mode from high beam mode. There must be a resistor inline somewhere to switch between the two voltages to the headlight. That would seem to need to take place with DRL relay number three but nothing is shown. Is there such a thing as DRL relay #2? I don't see one on the EWD.