Headlight Electrical Mystery LX470 (1 Viewer)

[fjryan]

Whilst leaving work the other night, I noticed that it was pretty dark in front of my 2003 LX470. I pulled back into a parking spot and found that both low beam headlights were not working. High beams worked fine and daytime running lights were good. I popped the hood to wiggle some wires and see if I could make the magic happen. I then discovered that the hood struts were weak and that in the cold weather, were insufficient to hold up the hood. FML. The wire wiggling didn't work. So I went to check the manual for fuse locations and when the hood slammed shut the driver side headlight came on. I opted to go home and trouble shoot the next day when I could get the truck inside.

Further troubleshooting got me some education on my new-to-me 100-series. Both headlights were good. Both fuses were good. Daytime running lights worked. When the truck is turned off, the head light switch in the on or auto position and the turn signal stalk pushed forward into the high beam position, the low beams work normally. When the switches are in the same position and the truck is running, the high beams come on. When the stalk is pulled into the mid (normal position) the low beams are completely off. When the light switch is rotated to the "off" position and the truck is on, the daytime running lights work.

I have and used the .pdf factory service manual for the 2004 Land Cruiser that I found on here. I don't know how much, if anything, is different from the LC to the LX but I imagine (hope) that it was not cost effective to re-engineer the electrical system. I couldn't figure out how to get to the engine compartment relay box to check the headlight relay. It appears to be on the bottom of the fuse/relay box but the wire bundles that run into and out of the relay box hold it down and I wasn't sure if the bundle ties/clips are reusable or if I need to get a replacement. Or if I'm doing it all wrong and there's some far easier method of cracking this nut.

If anyone out there has seen this or has any ideas, I'm all ears. I don't have a lot of experience with electrical issues but I have a decent academic understanding of how electrical systems work. I can follow instructions like a champion though. Thanks in advance.

-Franz

 

[TXLX100]

That's a strange one. I would check the battery grounds, the main fusible link and maybe go ahead and put a fresh fuse in for the headlights (fuses can partially break and be intermittent). It sure sounds like the stalk / switch though. You have power to the low beams if they work in high mode, so the wiring must be good back to that point. If you can look at a wiring schematic for the headlamp system and see if it's a dual input (for lack of better term) for the low beam system (if it gets signal from low beam and high beam on the switch). Has the windshield ever been swapped, any chance water could be running into the cab or fuse block?

 

[fjryan]

I'm not sure about the windshield, but I'll check the next time I'm outside and see if it says Toyota anywhere. I haven't seen any evidence of water intrusion but the fuse box gasket was toast. There was some mild oxidation on the fuse stalks but nothing major. I'll swap them when I get out there also and check it out. I don't currently have a detailed electrical schematic. The service manual doesn't go into detail on the stalk.

This is what I'm working with now. Any idea how I can access the relay to check it out? I'll also read into the manual and see what I can do to inspect of test the stalk. Thanks.

-Franz

 

[jerryb]

(fuses can partially break and be intermittent) that was me. Same issue, they would come on with a bump or after they warmed up, looked good but weren't.

 

[fjryan]

No joy with swapping the fuses, fellas. I'm back in the manual looking at the stalk.

 

[dogdaysindurham]

@fjryan , I think the daytime running lights at least on my LC are the high beams bulbs running at 1/2 regular voltage. I would suspect it would be the same on the LX. So if the low beam fuses were ok, it should be a bad low beam relay (labled HEAD in the fuse box picture below, the light blue one below the headlamp fuses). Per the FSM diagram posted, there seems to be a seperate high beam relay (ironically labeled DIMMER) in the fuse box picture below..

The replacement relay would be Denso 567-0005 maybe (but don't quote me on that).

This picture is from a 2001 LX470.

 

[dogdaysindurham]

@fjryan You could swap the DIMMER and HEAD relay to rule out the issue if you can't find a replacement relay to test. I believe they are both 40 amps, but haven't had a chance to verify. This goes off memory and the light blue coloring of the DENSO relay pictured above.

The next possible culprit is the control stock and in this FSM check out page 4923 (BE-26).

lc100-workshop-manual.pdf

 

[fjryan]

Well guys, my problem is solved. It was primarily in the drivers seat. When I checked the owners manual for the low beam bulb type it said 9006/55W/H1. When I was in the store I found 9006 type bulbs and stopped looking, not knowing that H1 bulbs are different. When I got back under the hood I found that the low beam bulb (H1) doesn't have the plastic 90 degree plug that the 9006 bulb does. But the high beam does! So I spent hours troubleshooting and looking for help for what turn out to be two burned out bulbs.

I appreciate you guys help though. Jerry, the link for the relay box fix was what I had been looking for. (In case someone else is on this thread looking for the answers: 2005 LX470 Main Junction Block Replacement). Dog Days, that manual you sent up is fantastic. It beats the snot out of the mismatched files that I had been using. I hope I have the chance to help out someone in the future.

 

[AZSlim]

@fjryan Thanks for following up on your post. I have exactly the same symptoms in my 99 LC and it's possible you just saved me a bunch of effort, will report back .

 

[AZSlim]

@fjryan Thanks for following up on your post. I have exactly the same symptoms in my 99 LC and it's possible you just saved me a bunch of effort, will report back .

Yep, both "low" (which are actually physically higher) headlight bulbs were burnt out.

So... in my personal experience, I've always witnessed 1 bulb going out before the other. Here, in multiple cases, we have both bulbs going out simultaneously (possibly only being noticed once both are out).

I'm no electrician... is it possible that when this happens it's indicative of a ground fault (or poor ground) in the low-beam circuit?

 

[fjryan]

Not sure. This is the first time I’ve dealt with it in this truck. If you’re having repeating issues then there’s probably some kind of issue. Or really bad luck with bulbs.