nor725

Hi,
I was changing my interior lights with led bulbs on my 2008 lexus ls460, whenl I briefly shorted out the courtesy light on the the passenger door courtesy light while changing the bulb. Afterwards, the 194 led light was dim on the passenger door while all the other doors and dome were bright. I ran a multi meter test and found that it was only giving 9v.
Can someone please help resolve this problem?
Any help is appreciated.

Nor725

Rhambler

Well, since you indicated that you "shorted" it, I would assume you might have partially melted that fuse, causing higher resistance and thus lower voltage, although typically these things just outright melt, although it is not unheard of for fuses to partially melt, thereby raising the resistance. Fuses have a melt time or clearing time and if the fault isn't high enough or long enough they could only partially melt (although this is rare). When this happens, the continuous current capability gets significantly degraded. And since there is less of an element in the fuse, the resistance goes up.

I have no idea if the lights are on individual fuses, but if they are, you might want to check that fuse. If they aren't, then it might be something else as you would get low voltage on all items off of that circuit if it was indeed the fuse. That low voltage tells me you have some abnormal (high) resistance somewhere in that circuit causing the voltage to decrease and it could be the wire, contacts, connections, socket, anything really.

Good luck.

nor725

Thank you for your reply Shambler, but I don't think it is the fuse as I tried replacing the fuse #23 for the passenger interior lights and I got same result. I heard though that the door latch switch only has a 9v , and I was guessing it is getting its power from there and that a controller or something which switches it to a 12v is broke. Just not sure where to find these things.

jmcraney

Check this thread to see if there is anything that might apply.

https://www.clublexus.com/forums/ls-...-led-swap.html

Chuckinnj

FIRST Go back to the factory bulbs then Check the voltage on the other doors ASAP after opening the door........ Hopefully you get 12 volts. Do the interior lights turn off after closing the doors?..... if not I hate to tell you that you "MAY" have fried the interior light controller module board, This controller ramps up and ramps down the voltage (up/down dimming) to the interior light bulbs.
Report back your results.
I do not know where the board is on the Lexus but I replaced this type of module on a Dodge Charger after a friend of mine fried his controller board after shorting a bulb socket and had similar problems with a low voltage to the bulbs.

nor725

Thanks JM Craney for the link you recommended. I suspect the post by BigWalt is applicable to my problem where he had to buy the multiplex door computer. But since everything works fine except for the 9v output on the passenger door courtesy light, I think I will just buy a led light with 8v-12v capacity. I hope it will be a little brighter than the led light I have currently installed. I have tried inter changing oem lights and led bulbs bought previously, but I came up with same result. I don't think though that paying $500 for this door computer is worth it, since the dome light is bright enough right now.
Thanks...


Originally Posted by BigWalt View Post
Ok so after many weeks of working long hours I was finally able to get my car to my cousin who was a Lexus tech.

Took it to the dealership with him on his day off.

Source of the problem was MULTIPLEX NETWORK DOOR COMPUTER Part number 89223-50300
about 500 dollars retail.

nor725

Also learned my lesson not to use any metal tool to help you extract the bulb as not to short anything. Fuses are easy to replace and cheap, but when it mess other items like a multi-plex network door computer and the hours trying to find the wiring connection is expensive and a pain.

GreggyG

I think my multiplex network door computer went bad also. Where is it located? My bulb is good and my door switch is good but there is only 9v going to the door connector when the door is open and then it actually raises a bit when I push in the door switch. So, there is a constant drain in my battery. What else could cause this? I don’t think it’s a bad ground because I also noticed that the oem bulb assembly plastic has weird discolored residue in it and therefore something must have happened to blow it out or short it in some way?

dfkd

It’s located inside the door.
Palm sized red box.

Mine failed when I shorted the lightbulb connectors while (foolishly) removing a bulb using a screwdriver while the housing was still connected.

I ordered a replacement on eBay.

Always unplug the light housing before removing the bulb.

GreggyG

Thank you, I found it

GreggyG

What does this unit control exactly? It has 3 plugs and a bunch of wires.

NotFasty

I have this same problem - driver side rear door light went 'bad' when I replaced a bulb. I've located the "multiplex network door computer" on Ebay but am not sure where it lives. Any pics or advice? Tried looking it up and no dice.

GreggyG

It’s located in each door and there is a different part number for each one

NotFasty

Thanks. Any idea how you reach it - does the inside door panel need to come off?