Hello, I'm having the same problem as the original poster. The dash lights (speedometer, tach) don't turn on when the headlights are on. I have a 2002 V6 Coupe. I haven't installed a new radio/speakers. For a few days I was able to turn the dash lights on by lightly banging on the dash, but now they are totally out.

I read through this thread and troubleshooted the following:

1) Changed fuses 10 & 7.5. The vanity and glove box lights do work.
2) The dimmer dial can control the clock.
3) I shorted the wires with a paper clip as explained in this video: .... lights still don't turn on. When I tested the dimmer with the paper clip inserted, the clock light did not dim, so I'm guessing the paper clip was inside correctly.

So in regards to #3 above, if this cheap fix didn't work, then is the problem not with the multiplex control unit?

I don't have an ohm checker but may get one if that's the only way to check other possible problems.

Any thoughts and tips are appreciated. My mechanic is saying that this could be a $400 job to diagnose/fix and I can't afford that right now.

Thanks for your help!

 

1. Just so we're talking on the same page, you changed the No. 10 (15A for coupe) in the passenger side fuse box and the No. 9 (7.5A) in the driver's side under dash fuse box? Why did you changed them, was a fuse blown or you just did it to try to make sure they were not?

2. You may want to pick up a voltmeter or multimeter to do some tests. At pin B22, where the Red/Blk wire is, check whether you have voltage when the combination switch is turned on. If not, you may have a problem with the combination light switch or wiring.

 

Hi redbull-1, thanks for your reply!

I changed out fuses 15A and 7.5A (located in the fuse box under the driver side dash) just to eliminate the fuses as a problem.

I'll look into getting a volt/multimeter as well to test what you suggested.

 

sometimes my dealer will give me free inspections...doesnt hurt to ask.

 

so i have a question on this, my accord is having the same issue i have checked all fuses, relays, made sure no wires were torn, i just seen this thread and was wondering, if it happens to be the MCU, which i will check tonight, and i replace it and leave the aftermarket stereo would it fry the computer again? because i would hate to pay for a new one and end up frying it.

 

It depends on the wiring of the aftermarket radio. Most aftermarket wire harness kits have a dash dimmer wire (generally it is an orange colored wire on aftermarket wire harness kits). If that orange wire from the aftermarket radio is hooked up to the car’s gauge cluster's dimmer wires, it can and will blow out the multiplex control unit (mcu). – Leave the aftermarket dash dimmer wire unconnected to make it simple.

The car’s dash light brightness control (dimmer – located in the gauge cluster) has two wires (a Wht/Red wire and a Red/Wht wire) which are bus communication wires leading to the driver’s mcu. Connecting a wire to these dimmer bus communication wires can blow out the mcu. In addition, hooking up any wire incorrectly to the red wires (which are the ground source wiring coming via the mcu) at any interior illumination that can be dimmed, can also blow out the mcu.

 

So after checking with the paperclip method my cluster did light up so apparently it is the mcu. Would you guys recommend getting a new one or a used one off ebay or a local salvage yard? Thanks

 

You'll probably get the best price at a salvage yard if you can find one.

 

anybody know what I have to do for a 1997 accord? Can I bypass the dimmer somehow like in that youtube video. I don't know if the wiring would be the same in a 1997

 

A 1997 is not the same and does not have a multiplex control unit. Please start a new help thread and describe your issue.