GL1200 A 1986 LCD pinout


Information and questions on GL1200 Goldwings (1984-1987)
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Motorbikebruno
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GL1200 A 1986 LCD pinout

Postby Motorbikebruno » Tue Aug 18, 2015 12:08 pm



Ok gents (and ladies). I've been a long time lurker on the forum and many posts have been helpful in my quest to fix my own bikes as well as friends and acquaintances too. You all have my gratitude for everything so far. Now, I've recently tuned up a friends GL1200 and she runs like a top. The side note here is that it sat since 2012 and there were mice all up everywhere. Some wires eaten etc. While on my test ride the LCD dash goes out. ALL of it. The only things still working are the lights on the sides which seem to come from a different part of the harness. I've got the bike fully apart and pulled the LCD gauges out in hopes to find something simple. After hours (days really) I've found a couple of posts informative but not my case.

This one states it was a fuse not allowing full voltage. I replaced (even though I was getting full voltage on both sides of the fuse, to no avail.
viewtopic.php?t=12067

Virgilmobile aslo put something saying add 12V to the dead circuit and see if that works. Well, after finding the Brown with black tracer wire carried power (can't find that post...but thanks to that person!!!) I have found 3 brown wires with black tracers going into the smaller white connector in the back of the LCD. 2 of them come from one harness, 1 comes from the other. The 2 coming from their own harness are OK and have the 12V the third is grounded....BUT when I apply 12V I get the dash to fire up it's starting sequence. So I thought all was well....not the case again. The fuel gauge is constant and OK. Nothing on the coolant section of the LCD, and the trip/gear indicator/speedometer/tachometer all flash around between what it SHOULD read and random other things. I fired the bike up and you could see the RPM doing what they should (intermittently between garbled stuff) and the gear indicator goes from neutral to 1 (again garbled) so all of that stuff is "working" but the gauge is "twitching."

So I tried adding 12V from a secondary battery and I think it fried something because I have no dash when I try the previous thing that got dash to light up. So a new LCD from ebay is in my future. But I thought I would share the current wiring pinout I've got and if anyone has more of these found, please feel free to add or PM me and I'll add them to the drawings. I JUST started on this so forgive me if it's crude :)
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virgilmobile
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Re: GL1200 A 1986 LCD pinout

Postby virgilmobile » Tue Aug 18, 2015 12:18 pm

I had one on my bench a few years ago.To bring the display active,it requires only one ground and 2 hot wires.One is constant 12 volts,the other is switched 12 volts.This will operate the computer through post.From there,active displays are rendered with input signals.
I'd retest on the bench before replacing the unit.All sensor inputs can be simulated.

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Re: GL1200 A 1986 LCD pinout

Postby virgilmobile » Tue Aug 18, 2015 12:36 pm

Here's a picture that might help...
Note:the one wire that shows "grounded"with the key off...It's most likely feeding a lamp...It will measure very low resistance...Solid red is normally constant 12 volts and Black/brown is switched 12 volts throughout the entire bike...
Be aware that a bad ground will upset the computer..Always use your DVM test points directly at the device and not a common frame ground.Should it have a poor ground for the PC board,the unit will try to find a better ground...sometimes through a sensor circuit...This would account for the erratic display.

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Re: GL1200 A 1986 LCD pinout

Postby Motorbikebruno » Tue Aug 18, 2015 12:38 pm

OK. I'll give that a shot and note them on the drawing for someone else's future use! Thanks a ton!!!

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Re: GL1200 A 1986 LCD pinout

Postby Motorbikebruno » Tue Aug 18, 2015 12:43 pm

Why not use the battery terminal for ground? I was hoping to use a small battery to test this on the bench as you say. -12V to the spot you call out on the above picture, and +12V to the contstant RED and keyed Brown/Black wire. Did I misread something?

Now I see why it's weird. On the 86, there isn't a separate 4 pin connector. Just the 2 going in....

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Re: GL1200 A 1986 LCD pinout

Postby virgilmobile » Tue Aug 18, 2015 12:58 pm

Using the frame or negative battery post for a ground reference assumes that the part that is being tested has a good connection to ground...Assume nothing..The displays ground goes through a few possible bad connections to get back to the battery...any one of them is suspect...
My rule of thumb...If a device needs volts to operate,always measure for that volts at the device.Both the positive and negative terminals.
Many times I have seen volts on a good lamp but the ground path corroded and it won't light..Measuring direct across the lamp shows no volts...Not a complete circuit...

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Re: GL1200 A 1986 LCD pinout

Postby Motorbikebruno » Tue Aug 18, 2015 12:59 pm

This is more like mine.
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Re: GL1200 A 1986 LCD pinout

Postby Motorbikebruno » Tue Aug 18, 2015 1:01 pm

virgilmobile wrote:Using the frame or negative battery post for a ground reference assumes that the part that is being tested has a good connection to ground...Assume nothing..The displays ground goes through a few possible bad connections to get back to the battery...any one of them is suspect...
My rule of thumb...If a device needs volts to operate,always measure for that volts at the device.Both the positive and negative terminals.
Many times I have seen volts on a good lamp but the ground path corroded and it won't light..Measuring direct across the lamp shows no volts...Not a complete circuit...



Ah, well I'm not testing it ON the bike. It's pulled out sitting on my table so I was going to use a separate battery (not attached to the bike of course!) and try to get it to live on the desk. Looks like I've got more work ahead of me than I thought.

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Re: GL1200 A 1986 LCD pinout

Postby virgilmobile » Tue Aug 18, 2015 1:13 pm

So can I guess that it had this erratic display on the bike only up to this point?
And you want to bench test it.?

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Re: GL1200 A 1986 LCD pinout

Postby Motorbikebruno » Tue Aug 18, 2015 1:39 pm

I was driving along on a test ride. All was well. Then all of the sudden I lost all LCD. It had blinked once or twice before outright failing. I took the connectors out of the left pocket and cleaned and moved them to see if it was a broken wire. Nothing. Wiggled and removed/reconnected wires all over the damn bike and nothing changed. Found the threads showing power with the Brown/black wires and after pulling the whole dash apart, I found that the gauge would "sort of" come to life with 12V applied to the one dead Brown/black wire on the right LCD connector. I was hoping someone had tested the LCD ALONE off the bike, but it appears that's not typical. :( :shock:

So yep, looking to bench test now. As I'm relatively certain each individual component is "working" from the one time I had it fired up I could read most of the parts but the actual numbers/letters flickered quite a bit when that happened.

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Re: GL1200 A 1986 LCD pinout

Postby virgilmobile » Tue Aug 18, 2015 2:00 pm

OK..I cant help much but I do have the same schematic you posted...I do see that the switched 12 volts on the Black/brown enters the plug with 9 connections and is harness jumped to the large plug with 13 connections...The other black/brown wires connecting to the display are switched 12 volts output to the sensors (like the spedo)...The red wire is 12 volts...On the green wire on the 9 conductor plug is the common ground...

It's interesting that you had volts on some black/brown wires but not on one of them...That would indicate that either the harness jumper is bad or there's a cold solder joint at the plugs on the PC board...Look close at each pin as it goes through the PC board for hairline cracks and resolder as necessary....Personally,if I see anything suspicious,I'll resolder them then apply 12 volts..

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Re: GL1200 A 1986 LCD pinout

Postby virgilmobile » Tue Aug 18, 2015 2:18 pm

There's probably just a couple of people that could bench test this display...Most just replace it hoping that it solves the problem.That's a 50/50 shot..I have operated a display on the bench using just the red and Black/brown for power and green ground..The display does go through self test and on the one I tested,the spedo showed Zero..I could pulse the input line and the readings would change.
It did have a bad IC that operated the bar graph display but the spedo and tach functions worked.

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Re: GL1200 A 1986 LCD pinout

Postby Motorbikebruno » Tue Aug 18, 2015 2:19 pm

virgilmobile wrote:OK..I cant help much but I do have the same schematic you posted...I do see that the switched 12 volts on the Black/brown enters the plug with 9 connections and is harness jumped to the large plug with 13 connections...The other black/brown wires connecting to the display are switched 12 volts output to the sensors (like the spedo)...The red wire is 12 volts...On the green wire on the 9 conductor plug is the common ground...

It's interesting that you had volts on some black/brown wires but not on one of them...That would indicate that either the harness jumper is bad or there's a cold solder joint at the plugs on the PC board...Look close at each pin as it goes through the PC board for hairline cracks and resolder as necessary....Personally,if I see anything suspicious,I'll resolder them then apply 12 volts..


Yeah, I'm trying to trace down which wires do what. It's going to take some time. I looked at all connections and I tell you, they all look pretty good. The Voltage regulator with the heatsink is looking a little warm, but not bad or burned up. I'll see what I can do and let you know what I find. I'm not sure what's more concerning though...the fact that it doesn't work, or that NONE of the electrical diagrams seem correct. There is no 12 pin connector, nor a 24 pin that is shown. There's a 14 position of which 10 are used, and a 20 position of which 18 are used. I'd like to punch the engineer in the face that wrote these diagrams right now....

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Re: GL1200 A 1986 LCD pinout

Postby virgilmobile » Tue Aug 18, 2015 2:36 pm

If you don't "see" anything..suspect the electrolytic caps.They do have a life span.
Don't spend a bunch of time trying to identify each connection.concentrate on power and ground.Get power to it and see what the display does.The use of a battery would be good...No noise on the power wires.Thats what the caps are for.Filtering and stabilizing.
I looked this up once.Most electrolytic caps have a lifespan of less than 2000 hours.This display has passed this limit.

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Re: GL1200 A 1986 LCD pinout

Postby Motorbikebruno » Tue Aug 18, 2015 3:09 pm

OK. I'll give it a go. I did find that my 14 pin connector on the gauge side is only a 13 pin on the other end due to a missing space. But that 24pin still doesn't make sense in the drawing :( haha I'll get one going from Ebay anyways. I'd like to see if it's LCD related or wire related on the motorcycle side either way.

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Re: GL1200 A 1986 LCD pinout

Postby virgilmobile » Tue Aug 18, 2015 3:13 pm

Keep us posted..take pictures.

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Re: GL1200 A 1986 LCD pinout

Postby Motorbikebruno » Tue Aug 18, 2015 3:41 pm

virgilmobile wrote:Keep us posted..take pictures.


Will do, and as you can see from my first post, I'm not shy about pictures. I think they help people so much, including myself.

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Re: GL1200 A 1984

Postby jayb » Thu Aug 20, 2015 11:03 pm

Virgilmobile. JayB again. I have a 1984 gl1200a that the last digit on the tac only works when it is warm. That is in the morning when it is cooler no last digit , If I let the sun shine on the dash here comes the last digit, Go figger. JayB

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Re: GL1200 A 1986 LCD pinout

Postby virgilmobile » Fri Aug 21, 2015 10:18 am

Very slight movement as the mounting frame expands when it gets warm.
The LCD glass uses a special method to electrically connect it to the copper connections on the PC board.
It's called a MOE or Zebra connector.Its a flexible strip of alternating insulator and conductive stripes.
On occasion,if they act up,the glass needs to me removed,the MOE cleaned,the copper conductors cleaned with a pencil eraser,etc,reassemble.
Or just live with it.
Depends on your level of OCD.

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Re: GL1200 A 1986 LCD pinout

Postby jayb » Fri Aug 21, 2015 10:28 am

Thanks Virgil, I will see how much it bugs me, I see that some of the 1200 have an alternative way of seeing the rpm other than digital I guess not on this one. JayB

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Re: GL1200 A 1986 LCD pinout

Postby Motorbikebruno » Fri Aug 21, 2015 10:30 am

As an update, I could not get the gauge to show up on the bench :( I got one off ebay, should be here early next week. I'll let you know how it goes, and whether the LCD is the issue on my particular bike, or if it's somewhere in the bike's harness that's to blame.




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