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Multiplexer unit

36K views 20 replies 9 participants last post by  nehonda 
#1 ·
my multiplexer is out. hell its been out for almost a year and a half now if not more actually. i havent been driving with any speedo lights. ive learned how to tell if im speedin or not. but i was wondering where in the world can i get one of these from? and i kno everyones gonna say a salvage yard. but where else besides dealership as well. those the only places that have em?
 
#4 ·
umm why was this moved?? from the 1998 accord section? oh well

and how exactly do i get to it and take it out? or am i already seeing it and just thinkin its somethin else?
 
#5 ·
If you're talking about the left multiplex control unit, it's in the back of the left fuse panel.

If you have an aftermarket radio, immediately remove any wires going to the illumination circuit of the CAR. These are NOT battery power and ground wires, they are bus communication lines to the factory radio's back lighting. By plugging those lines into the aftermarket radio, it blows out the multiplex box, and you lose all gauge back lighting.

I've probably seen more than a dozen gen 6 Accords with blown left side multiplex units, from improperly installed aftermarket radios. And nearly all were installed by stereo shops.
 
#8 ·
fred?? 100. 100% accurate... thats when mine happened. thing is nothin is connected to the dimmer switch. unless ur talkin about another wire.
 
#6 ·
This is the 98 Accord section (6th Gen) :wave:
I presume you have checked the fuses for the dash lights #10 and 13 in passenger fuse panel. The dash lights do use the drivers multiplexer unit located on the drivers side fuse panel to control the brightness and it is used for some other light controls also. There are some other multiplexers used in the car so be sure to get the right one. This one has a 24 pin connector according to the Honda service manual.

There is always ebay if you like to gamble on used parts (search for fuse panels - the multiplexer usually comes with it).

Good Luck
 
#9 ·
Im not a Honda electrical engineer so I cant tell you exactly how they work, but the service manual has a full page description if you have access to one. Here is a shortened version.
The main purpose is to reduce the number of wires in a harness by sending multiple signals down the same wires. There are about a dozen circuits that are multiplexed. Mostly timers, reminder chimes, power door locks and windows, wipers, dash light brightness, transmission interlock, keyless entry, etc. The CPU converts the inputs to digital signals and sends them to the recievers as serial signals where it is converted to a switch signal which operates the device. The system has wake-up and sleep modes for reduced power consumption, fail safe modes for faulty connections or modules and its own DTC system for troubleshooting.
 
#11 ·
If you mean instrument back lighting, there are 12v sources, one being the shifter light in the console on autos. There is also 12v sources on the back lighting for the cruise switch or fog light switch on the left side of the steering wheel. These will dim with the dimmer.

However, if you have something that's a fairly high draw, you're going to have to put a relay in the circuit.
 
#15 ·
You shouldn't need to put a relay in for the radio's back lighting, but DON'T hook it to the "illumination" wires at the factory stereo's plug. You'll have to find that 12v source at another location, that's all.
 
#16 ·
fred!!! which wire are u talkin about. theres nothing connected to my dimmer switch
 
#17 ·
the dimmer in the cluster doesn't directly dim the lights outside the cluster, it sends a "request" so to speak to the multiplexer to signal the other parts, such as the factory radio and a/c controls to dim or brighten.

The other lights that operate at 12v are the back lights for the console shifter, and the fog light switch or cruise control switch. The glove box light should also get 12v when the parking lights are on as well.

They all get 12v when in parking light position, but are ground controlled through the multiplexer.

The two wires leading from the dimmer knob in the cluster are "bus" wires leading to the multiplexer, hooking anything to these will burn out the multiplex unit. Same goes for hooking anything incorrectly to the ground controlled solid red colored wires at any lights that dim with the dash light brightness control.

The red/black wire leading to these things are the + battery wires leading to the components.
 
#18 ·
ok im not sure if youre saying the same thing im thinking but.... are you talkin about the orange wire coming from behind the radio in the wire harness?? if so then nothings hooked to it. and never has been. but... if youre not then pshhh i get it but dont see why it would blow my cluster...
 
#20 ·
hmm...mines orange...unless. ahh id have to go look and ill post up what i see
 
#21 ·
Per the Accord service manual the audio unit has a red/black wire connected to the combination light switch on LX and DX cars. On the EX that wire is connected to the tail light relay. The red and blue wires go to the multiplexer, so you probably dont want to mess with those. The circuit diagram doesnt show any orange wires.
 
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