I have 2004 Lexus LX. Recently the headlights have become possessed by some sort of electrical demon. After 5 - 10 min of nighttime driving the high beams will flash on by themselves. Most of the time they literally flash, very rapidly, on and off. Sometimes they will stay on high beam for several seconds or minutes but most of the time it's a very rapid flashing. With the engine off, for example in the garage while the lights time off after a drive you can hear a clicking on and off that seems to come from the engine bay fuse box. I suspect some sort of relay is bad but the fuse box lid has no location for a headlight relay. Any thoughts? All help is greatly appreciated.
Headlights Gone Wild (1 Viewer)
- Thread starter Sirmatthewt
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Has it been raining there? Have you taken it through the carwash?
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- #3
It had rained quite a bit before it started but it hadn't rained in a day or so when it started last Wednesday and really hasn't been driven in the rain since.
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Yeah. If I can I might try to take a video of it. It's weird. The high beams flash way faster than you could ever flash them manually with the stick. Very audible clicking on and off from somewhere inside the engine bay junction box. High beam indicator on the dash also flashes on and off. If you move the stick to high beams they stay on just like normal. I end up just switching the high beams on but eventually I, or my more likely my wife, is going to get stopped for driving around town with the high beams on (or for flashing them uncontrollably). Apparently no one has a solution for this. Nothing online. Waited 48 hours on JustAnswer. Crickets. I can't even find any info on where a headlight relay on the 100 series might be. I suppose it might be the DRL relay but that's not where the audible switching on and off is coming from. My fear is that the headlight relay is built into the fuse/relay junction box. The multi-switch is also a definite possibility but it works fine otherwise and I hate to just start throwing expensive electrical components at it.
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Which relay? And where?
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Found a .zip file service manual on the forum. Apparently, the HL relay is in fact built in to the relay block/wiring harness. Joy. As is the horn relay by the way, which is even more awesome. How fun would it be to replace a $600+ part because the stupid horn is going haywire.
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Anybody have any idea what the part number for the engine room junction block is? Hopefully, it's stamped on the block but I'm not with the vehicle. Suggestions on where to find one at the best price?
it's probably on the cover, pull it and if the High Beams no longer work, you've got the right one. Then, find a similar one and try it in the high beam relay's spot, and see if you get the same issues.
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From the .zip filed service manual:
4. INSPECT ENGINE ROOM R/B RELAY CIRCUIT (See
Pase BE-15 )
HINT:
The (Headlight, DIM, Tail relay) is built in engine room junction
block. Also the relay is constructed with a relay block that is in
the junction block as a unit. To disconnect the wire harness connecting
with relay block is impossible. If the relay has a malfunction,
replace it with junction block assembly wire harness together.
A $750 list priced part.
4. INSPECT ENGINE ROOM R/B RELAY CIRCUIT (See
Pase BE-15 )
HINT:
The (Headlight, DIM, Tail relay) is built in engine room junction
block. Also the relay is constructed with a relay block that is in
the junction block as a unit. To disconnect the wire harness connecting
with relay block is impossible. If the relay has a malfunction,
replace it with junction block assembly wire harness together.
A $750 list priced part.
- Thread starter
- #12
The thing is I'm not certain that it's the relay. The clicking on and off is definitely coming from the relay block. However, it is possible the relay is being energized to switch the high beams on and off by a fault or short elsewhere in the headlight system. With no way to actually swap out the relay to check this I'm at a loss for where to start. Spend the $500+ dollars to replace the whole block and possibly not fix the gremlin? I don't know. Someone smarter than me could probably check resistance, etc etc on the whole circuit and trace it down but I'm pretty sure that person is not me.
Here you go....
2004 LEXUS LX470 Block assembly, engine room junction. Block assy, engine r. Block assy - 8272060081 | Butler Lexus of South Atlanta Parts, Union City GA
It appears to be same part number for both Toyota and Lexus.
Do you by any chance have HID bulbs and installed? Eliminate the simple things first.
2004 LEXUS LX470 Block assembly, engine room junction. Block assy, engine r. Block assy - 8272060081 | Butler Lexus of South Atlanta Parts, Union City GA
It appears to be same part number for both Toyota and Lexus.
Do you by any chance have HID bulbs and installed? Eliminate the simple things first.
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- #14
No, no HID's. I'm wondering about the multi-switch on the column. It seems a much more like spot for a short than the relay that's built into the junction block.
The problem with the headlights is that it is on the Multiplex system, if you have no experience diagnosing this type of system I would leave it alone, you can do more harm than good. If you have techstream maybe there is a parameter to read in the body ECU to help eliminate the switch, from there it is just 0's and 1's to your engine room JB and then hard wired to the lights.
Check for water on your Body ECU in your left hand kick panel, this is the systems biggest weakness.
So the circuit is hard wired from combination switch to body ECU, multiplex to engine JB, then hard wired to lights.
Check for water on your Body ECU in your left hand kick panel, this is the systems biggest weakness.
So the circuit is hard wired from combination switch to body ECU, multiplex to engine JB, then hard wired to lights.
Ignore what I said, I have found a wiring diagram and I can't see any multiplex lines in the system, it said it is in the system but it might just be internally on the body ECU. Here is what I found.
$474 shipping included from part souk.
If you need a combo switch #84140-33020 switch/ interrupter I have one sitting here I'll sell for cheaper than anywhere else.
I looked into this when my low beams wouldn't come for a minute or longer. Turned out the fuse was just dirty. It's probably not the switch but you never know.
This is someone elses vehicle. 2005 LX470 Main Junction Block Replacement
If you need a combo switch #84140-33020 switch/ interrupter I have one sitting here I'll sell for cheaper than anywhere else.
I looked into this when my low beams wouldn't come for a minute or longer. Turned out the fuse was just dirty. It's probably not the switch but you never know.
This is someone elses vehicle. 2005 LX470 Main Junction Block Replacement
Do you have the lights on “automatic “? If so, go manual on. Start simple...
To be honest, if I am getting your problem right. The high beam comes on, on its own when driving, not your normal headlight but the full beam(flash). Sorry but we call the headlights different in the UK, we use side, dipped and main beam terminology. If it is your hi/flash/main beam, I would look at your body ECU as this grounds your hi beam relay in your engine room JB. If the relay is clicking then it has to be getting the ground signal from your Body ECU or your cable is damaged, as a relay won't energise without power and ground. If it is your normal headlights that start flashing then it could be between body ECU, engine room JB or automatic light control.
