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Retired Nuclear Engineer
2006 GL1800 Comfort/Navi
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6 Posts
Discussion Starter #1
I know the LCD displays have been discussed quite a bit, and I've read them all - trust me. A couple of years ago, my LCD screen started getting dim to where the backlight was visible only in low light or at night, even with the dim setting on the bike at max. I ordered a replacement (foreign) and changed it out after sitting on it for about 4 months. There was no improvement; it wasn't any brighter. I ordered another supposedly OEM replacement, again from overseas, and again, no improvement. I did some research, and I ordered just the CCFL tube from a US manufacturer, and I replaced just the tube, again with no change in brightness. So my troubleshooting background tells me that if 4 displays give the same problem, it's probably NOT the LCD display, but the power being supplied to the CCFL tube. I've gone through every relevant schematic in the GL1800 Electrical Troubleshooting manual, and the "Combination Meter" as they call it has inputs and outputs, but they do not provide a schematic of what's inside the "Combination Meter", which contains the gauges and a circuit board. My theory is that the circuit board provides the power for the CCFL tube, and is probably not putting out as much power as it should. (And on a side note, the power to the CCFL is NOT DC.) I would LOVE to be able to get hold of another circuit board, because I'm sure that's most likely my issue. I welcome any input!
 

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Administrator
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26,157 Posts
It's been a grip of mine for a long time that they (Honda) don't supply any info on the internals of any electronic component. Do the back lights of the instruments work OK?
 

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Retired Nuclear Engineer
2006 GL1800 Comfort/Navi
Joined
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6 Posts
Discussion Starter #3
The instrument lighting is fine. My only issue is with the LCD screen.I tried an experiment with one of the panels I tried. I modified it, substituting a high intensity LED strip for the CCFL tube. It did a great job when I hooked the strip up to DC, only to learn the hard way that the bike does not provide DC to the CCFL tube, but a high frequency voltage of some sort. I guess I could've researched it a bit more first. Or I could've improvised a DC control to the backlight, but that's not how I roll.
 

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Retired Nuclear Engineer
2006 GL1800 Comfort/Navi
Joined
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6 Posts
Discussion Starter #4
Well I have some news on my posts about my LCD screen. I had supposed that my circuit board providing power to the LCD screen was not putting out the appropriate power any more, which is why my screen was dim. By carefully watching Ebay, I finally found a 2007 GL1800 instrument panel from a wrecked GW for sale. It looked pretty banged up, but the seller said it still worked and the screen worked ok. I bought it with expectations I could change out the circuit board and that would fix the problem. I also now had a genuine Honda LCD screen if needed. I first changed out the circuit board and was surprised that my screen was no brighter! 😕 So I put my original board back in, and swapped the LCD screen. Wow! Much brighter. I downloaded an app on my phone to measure the relative intensity of the screens. My original came in at 13 lumens. The screen now had 77 lumens! Bingo! It was the backlight behind the screen all along! So I now had intensity, BUT the screen had some damage from the wreck, and there were several horizontal lines that were evident. So I was bummed. But after thinking about it, I figured that I could fix it by removing the backlight from the damaged OEM screen and install it into the $100 screen from China where the pixels were all in good shape. Carefully I made the swap and put the OEM backlight into the good screen. And now it was finally fixed!!! I have great brightness, and the screen looks like new.

What I learned: The cheap replacement screens from overseas work, but the backlights (at least on the 2 I bought) are not up to par, and the brightness will leave you with a dim screen. Also while swapping things around and testing, I was using the functional speedometer set that I got from the Ebay purchase. The mileage you see on your screen is stored in the speedometer. The mileage was 56K on the Ebay instruments. When I tried the Ebay circuit board (with speedo), I was seeing 56K miles. But when I put my original circuit board back in, I still was seeing 56K! My heart sank, wondering if once the "bike" saw 56K, there was no going back. But as it turned out, it was just because I still had the Ebay speedometer hooked up. As soon as I put my speedo back in, the mileage went back to the 32K it was supposed to show. Whew! Figuring things out by trial and error can be nerve-wracking, but fortunately, all this came out ok, and the bike is fixed.

One last note, swapping out the backlight was tedious, but not that difficult if you take care while you're doing it. If you can remove the speedometer assembly and change out the LCD screen, you should have the necessary expertise to swap the backlight.
 

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Thanks for reporting. Too often when the problem gets fixed we hear no more from the original poster.
 
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