Starts and runs but no headlight or instrument lights


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Blueten99
Posts: 8
Joined: Sat Feb 13, 2021 4:15 pm
Location: Sioux Falls, SD
Motorcycle: 1984 Honda GL1200I Interstate

Starts and runs but no headlight or instrument lights

Post by Blueten99 »



I recently purchased a 1984 GL1200 Interstate and I'm stumped. The bike starts and runs with no issues but I have no headlights, tai lights, or dash lights and the tach does not work. When I turn on the ignition switch, I get power to the fuse box and the accessory lights work. I tested the wires coming off the ignition switch and with the key turned on, I did had power only to the fuse box so I figured it was a bad ignition switch so I got one off ebay (used OEM part and trusted the seller when said it was tested) but I have the same exact problem with the second ignition switch. The bike is in superb condition otherwise with low miles. I was able to get wiring schematics posted on this site (thank you thank you) and purchased a good volt meter. I've checked every connection I could see but I must be missing something. Any ideas?


Techdude2000
Posts: 469
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Location: Lexington, KY
Motorcycle: 2004 GL1800

Re: Starts and runs but no headlight or instrument lights

Post by Techdude2000 »

Blueten99 wrote: Sun Aug 01, 2021 8:00 pm I recently purchased a 1984 GL1200 Interstate and I'm stumped. The bike starts and runs with no issues but I have no headlights, tai lights, or dash lights and the tach does not work. When I turn on the ignition switch, I get power to the fuse box and the accessory lights work. I tested the wires coming off the ignition switch and with the key turned on, I did had power only to the fuse box so I figured it was a bad ignition switch so I got one off ebay (used OEM part and trusted the seller when said it was tested) but I have the same exact problem with the second ignition switch. The bike is in superb condition otherwise with low miles. I was able to get wiring schematics posted on this site (thank you thank you) and purchased a good volt meter. I've checked every connection I could see but I must be missing something. Any ideas?
Does the fuel gauge work?
Blueten99
Posts: 8
Joined: Sat Feb 13, 2021 4:15 pm
Location: Sioux Falls, SD
Motorcycle: 1984 Honda GL1200I Interstate

Re: Starts and runs but no headlight or instrument lights

Post by Blueten99 »

I don't believe the fuel gauge works either but I don't recall so I'll double-check after work today and let you know - thank you for the reply
Blueten99
Posts: 8
Joined: Sat Feb 13, 2021 4:15 pm
Location: Sioux Falls, SD
Motorcycle: 1984 Honda GL1200I Interstate

Re: Starts and runs but no headlight or instrument lights

Post by Blueten99 »

No, the fuel gauge does not move, either. It's like there must be a fusible link or something that I'm missing. I saw other posts referencing the run switch but I don't know. What really sucks is when I picked up the bike, all the lights were working. I drove it home and ordered the carb kits to fix a minor leak under carb 3 but they are sitting on a shelf along with and a 4-port vacuum gage to balance the carbs but when I was out driving it for the second time, maybe twenty minutes in, I lost the lights. Took it home and parked it and when I went out to look at it again, the lights worked again but then stopped working maybe five minutes later and haven't worked since. I have run a positive wire directly from the battery via a toggle switch, bypassing the ignition and I can get all the lights to come on which is why I was pretty sure it was the ignition switch. Maybe the ebay ignition switch was bad and I shouldn't have taken his word for it. I'm sure I can jury rig the whole thing and use the spare accessory output to power the gauges but worry about what I could be frying since I'm electronically ignorant (give me carburetors any day) - I'm hoping you can point out something obvious and appreciate the consideration a lot! Looks like this one is going to be another project bike.
Techdude2000
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Location: Lexington, KY
Motorcycle: 2004 GL1800

Re: Starts and runs but no headlight or instrument lights

Post by Techdude2000 »

Blueten99 wrote: Wed Aug 04, 2021 5:50 pm No, the fuel gauge does not move, either. It's like there must be a fusible link or something that I'm missing. I saw other posts referencing the run switch but I don't know. What really sucks is when I picked up the bike, all the lights were working. I drove it home and ordered the carb kits to fix a minor leak under carb 3 but they are sitting on a shelf along with and a 4-port vacuum gage to balance the carbs but when I was out driving it for the second time, maybe twenty minutes in, I lost the lights. Took it home and parked it and when I went out to look at it again, the lights worked again but then stopped working maybe five minutes later and haven't worked since. I have run a positive wire directly from the battery via a toggle switch, bypassing the ignition and I can get all the lights to come on which is why I was pretty sure it was the ignition switch. Maybe the ebay ignition switch was bad and I shouldn't have taken his word for it. I'm sure I can jury rig the whole thing and use the spare accessory output to power the gauges but worry about what I could be frying since I'm electronically ignorant (give me carburetors any day) - I'm hoping you can point out something obvious and appreciate the consideration a lot! Looks like this one is going to be another project bike.
Ok, first off, let me tell you up front that I’ve never worked on a 1200 wing, but I have been reading schematics for 38 years. With that said, your key switch is working or the engine wouldn’t run. The same power wire that feeds the fuel pump relay also feeds the fuse block that has the tail light, headlight, and other various fuses. Any time the key is on, you should have power on those fuses. It’s hard to tell the color, but I believe the switch feeds them from the black wire(far right on the switch diagram) which is spliced and runs to a lot of places. Some of those places are getting power, but others are not. The first thing I would do is find the black wire that feeds the fuses and see if moving it around near the fuse block makes the fuses get power. If you look at the diagram, the black bar that runs across under the fuse box is a connector somewhere and may have corrosion in it as well. I just reread your first post, do you have power in the fuse box or not when the key is on? If you do, then you definitely need to locate that connector.
Blueten99
Posts: 8
Joined: Sat Feb 13, 2021 4:15 pm
Location: Sioux Falls, SD
Motorcycle: 1984 Honda GL1200I Interstate

Re: Starts and runs but no headlight or instrument lights

Post by Blueten99 »

To clarify, I have 12.4 V off the accessories out from the fuse box when the key is turned on. I think you are getting me in the right direction though, I did not check if I was getting power off all the rest of the fuse outputs when the key is turned on. I will check that next and yes, I see the power line/connection points on the schematic that you are referring to. I also understand why when I ran a cable from the battery to what is essentially the power out from the fuse box (excuse the non-electical terminology) that I got lights/power. I'm probably lucky I didn't smoke anything by bypassing the fuse box. I guess I assumed that if I had power to the accessories that the rest of the fuses were getting power. I'm starting to understand wiring schematics better (in my dreams).

Assuming I have power out of the fuse box, I will look at what must be a connector that feeds the "dash" and headlights and see if I get power there. I hope I can find the connection without having to take the fairing off. Seeing things on a diagram is not the same as finding the parts on the bike, that's for sure. I'm curious about that 7v Regulator on the diagram, too. I'm not sure what that thing does but it doesn't look like it has any connections in common with the headlight power so I assume that can't be the issue.

I truly appreciate your input. 38 years of reading wiring diagrams...great!! I will test this weekend (probably sooner, as I like the "detective" aspect of all this) and will report back what I find.
Techdude2000
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Location: Lexington, KY
Motorcycle: 2004 GL1800

Re: Starts and runs but no headlight or instrument lights

Post by Techdude2000 »

Blueten99 wrote: Wed Aug 04, 2021 8:30 pm To clarify, I have 12.4 V off the accessories out from the fuse box when the key is turned on. I think you are getting me in the right direction though, I did not check if I was getting power off all the rest of the fuse outputs when the key is turned on. I will check that next and yes, I see the power line/connection points on the schematic that you are referring to. I also understand why when I ran a cable from the battery to what is essentially the power out from the fuse box (excuse the non-electical terminology) that I got lights/power. I'm probably lucky I didn't smoke anything by bypassing the fuse box. I guess I assumed that if I had power to the accessories that the rest of the fuses were getting power. I'm starting to understand wiring schematics better (in my dreams).

Assuming I have power out of the fuse box, I will look at what must be a connector that feeds the "dash" and headlights and see if I get power there. I hope I can find the connection without having to take the fairing off. Seeing things on a diagram is not the same as finding the parts on the bike, that's for sure. I'm curious about that 7v Regulator on the diagram, too. I'm not sure what that thing does but it doesn't look like it has any connections in common with the headlight power so I assume that can't be the issue.

I truly appreciate your input. 38 years of reading wiring diagrams...great!! I will test this weekend (probably sooner, as I like the "detective" aspect of all this) and will report back what I find.
The 7 volt regulator runs the fuel and temp gauges. It gets its power from the fuse box to regulate down to 7 volts for those gauges. It actually shares the 12V for the headlights and the tachometer coming from the fuse labeled “Oil/Highbeam” The accessory out terminal gets its power from a different wire coming from the key switch, but the wire that feeds the rest of the fuses feeds the fuel pump relay and the ignition coils through the kill switch, so we know it has power on it to make the engine run. It has to be getting lost on the way to the fuse box.
Blueten99
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Joined: Sat Feb 13, 2021 4:15 pm
Location: Sioux Falls, SD
Motorcycle: 1984 Honda GL1200I Interstate

Re: Starts and runs but no headlight or instrument lights

Post by Blueten99 »

OK, I tested. I have five fuses marked on the fuse box diagram:
- Accessories: has 12.4V at the fuse
- Head: has less than 1V (40-45 mV) at the fuse
- Meter Tail: has 12.4V at the fuse
- Horn Turn Stop: has 12.4V at the fuse
- Neutral Oil: less than 1V (10-15 mV) at the fuse
How I measured voltage was using the body ground on the frame, pulled the fuse and measured on the power-in side of where you would plug in the fuse.
I cleaned the connection into the fusebox with a razor and 400 grit as best I could but pretty sure if the larger green ground wire or the larger black wire on the connection to the fusebox was not a good connection, all five fuses would be less than 1V. The rest of the wires would be the output wires of the fusebox and I think I should solve the problem with the power-in side of those fuses and measure the output later as needed.
When I was positioning the volt meter so I could see the display (you probably know this, but get a voltmeter with a stand...live and learn), I moved the fusebox out of it's plastic holder and the bottom of the fusebox was noticeably warm to the touch. Not like smoking hot, but very warm. I'm guessing that should not be the case.
So I have power into the fuse box, power in and out on 3 of the 5 fuses but no power in on 2 of the fuses and the bottom of the fusebox is warm. The box itself is sealed so I can't pull the bottom off to inspect the internals of the box but I'm pretty sure I know where the problem is. What do you think?
Side note...when you explained what the 7V Regulator is for, a light went off...I have an 82 Aspencade that had a damaged front fairing (as in seriously broken fiberglass and bent up mounts) that I ended up making into a bagger which (thank goodness) didn't have any electrical issues except that the fuel and temp gauges always read about 40% higher than they should. Wasn't worried about it but has bugged me for months. I'll bet if I dig deeper on that I will find that I bypassed the 7V regulator and the gauges are getting battery voltage. They worked before I stripped it down. So double-thank you for that explanation. Thank you Thank you.
Techdude2000
Posts: 469
Joined: Mon Jun 13, 2011 10:11 pm
Location: Lexington, KY
Motorcycle: 2004 GL1800

Re: Starts and runs but no headlight or instrument lights

Post by Techdude2000 »

Blueten99 wrote: Fri Aug 06, 2021 9:03 pm OK, I tested. I have five fuses marked on the fuse box diagram:
- Accessories: has 12.4V at the fuse
- Head: has less than 1V (40-45 mV) at the fuse
- Meter Tail: has 12.4V at the fuse
- Horn Turn Stop: has 12.4V at the fuse
- Neutral Oil: less than 1V (10-15 mV) at the fuse
How I measured voltage was using the body ground on the frame, pulled the fuse and measured on the power-in side of where you would plug in the fuse.
I cleaned the connection into the fusebox with a razor and 400 grit as best I could but pretty sure if the larger green ground wire or the larger black wire on the connection to the fusebox was not a good connection, all five fuses would be less than 1V. The rest of the wires would be the output wires of the fusebox and I think I should solve the problem with the power-in side of those fuses and measure the output later as needed.
When I was positioning the volt meter so I could see the display (you probably know this, but get a voltmeter with a stand...live and learn), I moved the fusebox out of it's plastic holder and the bottom of the fusebox was noticeably warm to the touch. Not like smoking hot, but very warm. I'm guessing that should not be the case.
So I have power into the fuse box, power in and out on 3 of the 5 fuses but no power in on 2 of the fuses and the bottom of the fusebox is warm. The box itself is sealed so I can't pull the bottom off to inspect the internals of the box but I'm pretty sure I know where the problem is. What do you think?
Side note...when you explained what the 7V Regulator is for, a light went off...I have an 82 Aspencade that had a damaged front fairing (as in seriously broken fiberglass and bent up mounts) that I ended up making into a bagger which (thank goodness) didn't have any electrical issues except that the fuel and temp gauges always read about 40% higher than they should. Wasn't worried about it but has bugged me for months. I'll bet if I dig deeper on that I will find that I bypassed the 7V regulator and the gauges are getting battery voltage. They worked before I stripped it down. So double-thank you for that explanation. Thank you Thank you.
Yep, sounds like an issue in the fuse box. Heat in a fuse box is not a good thing for sure. Maybe you can cut the seams to get it open, then glue it back together with ABS cement or melt it back together with a soldering iron(not good for the tip, but works). Maybe someone else on the board has gotten one apart and can shed some light on it.
Blueten99
Posts: 8
Joined: Sat Feb 13, 2021 4:15 pm
Location: Sioux Falls, SD
Motorcycle: 1984 Honda GL1200I Interstate

Re: Starts and runs but no headlight or instrument lights

Post by Blueten99 »

I found some exact match used OEM fuseboxes on ebay for under 20$ so I'll replace the box instead and start working on the carbs. I'll post back here in a couple of weeks to confirm it worked. I would not have figured this out on my own. I can look at a wiring schematic now and not be quite so intimidated. Wonder why schematics don't show the directional flow of electricity. They would sure be easier to figure out if they did. Otherwise it seems the trick is to remove assumption and apply logic and/or rely on the experience of others.

I've been riding for over 40 years but pretty much only 3 different bikes. I've had my 84 700 Magna which is an amazing vehicle for over 10 years but it's a city bike. I've had a crush on the GL1200's for years. Not to say the 1500 and 1800's aren't gorgeous, but the lines on the 1200 hit home for me so when someone totalled my old ratty pickup truck and I got way too much money from their insurance company, in the middle of January, on what was literally the coldest day of the year (-23 degrees), I went to a dealership that brokers bikes. I could see the obvious carb issue on the silver GL1200 but you could tell it was cared for. One tiny little scratch on the fairing, another on the front fender and some flaking pin stripping on the side bags, otherwise it looked new with under 40K miles and I got it for $1235. Back in the dark corner of their floor was the damaged Aspencade. When I got home, I kept thinking why not? To me the carbs on the 1200 were a non-issue, but the 1100 was obviously a full out project. I went back 2 hours later and bought the brown "Moose" for $400, too. An agonizing two months later on a warm March day, I drove them both home. The 1200 was beyond what I thought it would be like to drive, smooth, powerful and no vibrations but the 1100 with bent up forks and wobbly front wheel was a 10 mph adventure to drive the 3 miles home. Then the electric issues and being stumped for literally months, I worked on the 1100. By the beginning of May, the Moose was on the loose, now a roadworthy bagger, rolling so smooth I can no-hand it all day long and the 1200 just sitting there waiting for some guy from Kentucky to point me in the right direction. Thank you again.
Techdude2000
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Location: Lexington, KY
Motorcycle: 2004 GL1800

Re: Starts and runs but no headlight or instrument lights

Post by Techdude2000 »

Blueten99 wrote: Sat Aug 07, 2021 9:57 am I found some exact match used OEM fuseboxes on ebay for under 20$ so I'll replace the box instead and start working on the carbs. I'll post back here in a couple of weeks to confirm it worked. I would not have figured this out on my own. I can look at a wiring schematic now and not be quite so intimidated. Wonder why schematics don't show the directional flow of electricity. They would sure be easier to figure out if they did. Otherwise it seems the trick is to remove assumption and apply logic and/or rely on the experience of others.

I've been riding for over 40 years but pretty much only 3 different bikes. I've had my 84 700 Magna which is an amazing vehicle for over 10 years but it's a city bike. I've had a crush on the GL1200's for years. Not to say the 1500 and 1800's aren't gorgeous, but the lines on the 1200 hit home for me so when someone totalled my old ratty pickup truck and I got way too much money from their insurance company, in the middle of January, on what was literally the coldest day of the year (-23 degrees), I went to a dealership that brokers bikes. I could see the obvious carb issue on the silver GL1200 but you could tell it was cared for. One tiny little scratch on the fairing, another on the front fender and some flaking pin stripping on the side bags, otherwise it looked new with under 40K miles and I got it for $1235. Back in the dark corner of their floor was the damaged Aspencade. When I got home, I kept thinking why not? To me the carbs on the 1200 were a non-issue, but the 1100 was obviously a full out project. I went back 2 hours later and bought the brown "Moose" for $400, too. An agonizing two months later on a warm March day, I drove them both home. The 1200 was beyond what I thought it would be like to drive, smooth, powerful and no vibrations but the 1100 with bent up forks and wobbly front wheel was a 10 mph adventure to drive the 3 miles home. Then the electric issues and being stumped for literally months, I worked on the 1100. By the beginning of May, the Moose was on the loose, now a roadworthy bagger, rolling so smooth I can no-hand it all day long and the 1200 just sitting there waiting for some guy from Kentucky to point me in the right direction. Thank you again.
Glad I could help. They don’t put current or voltage directions on schematics, because if you really followed the current direction it would confuse most folks. Current flows from ground to the positive side of all circuits that are negative grounded. When you see that on a diagram it looks completely backward from conventional thought, but in the real world it flows that way. Some people will argue the point until they’re blue, but all the proof required is a traditional TV picture tube, or CRT. The guns in the back have a very small positive voltage on them and the screen(shadow mask) inside the face of the tube has a very large positive voltage. When the system lights up the screen, it’s done by the electrons(current) flowing from the guns toward the screen and exciting the phosphorus on their way to the mask. They are directed by a magnetic field inside the tube’s neck that steer the electron beam in a sweeping left to right and top to bottom motion. This is raw electron flow(current) and you can’t see it, you can only see the result of it hitting the phosphorus. The same thing happens in a piece of wire, the current flows from the negative or less positive to the positive or more positive side of the circuit. So here’s a thought using these facts. All of the current that your starter motor uses to spin the engine leaves the battery’s negative terminal and travels through the frame/engine block through the starter motor case, armature, field windings, and brushes, and then back to the starter relay(s) and on to the positive battery post every time you push the starter button. :shock:
Blueten99
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Motorcycle: 1984 Honda GL1200I Interstate

Re: Starts and runs but no headlight or instrument lights

Post by Blueten99 »

Yeah, I would be one of those "blue in the face" guys, I'm sure.

So to apply your kind explanation to that wiring schematic, the only way to tell if a wire should have current is to track backwards (technically forwards). For instance, on that diagram, there is a red wire that goes from the battery positive to the main fuse. Then from the main fuse another red wire goes to the ignition switch and when the key is "on" current flows though the black wire to the fusebox (with the understanding that technically, the current flow starts at the green ground wire). When the switch is "off", the current just flows from the ground back to the battery via the red and green wires and/or does nothing.

Where I got so head pounding confused was that if you keep following that black wire it also goes to the regulator/rectifier which I mistakenly assumed was the source of the current to the fusebox. Instead, if I'm on the right track, the current to the fusebox does not rely on the rectifier/regulator at all. If I disconnect that black wire from the regulator/rectifier, as long as the battery has power and the key is turned on, the fusebox would have current, correct? The schematic would also imply that for whatever reason, the key has to be turned on and the rectifier/regulator have positive current on that black wire to function correctly, correct?

Anyway, I didn't mean to get into this so deep, but for me, this is eye-opening.
Techdude2000
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Motorcycle: 2004 GL1800

Re: Starts and runs but no headlight or instrument lights

Post by Techdude2000 »

Blueten99 wrote: Mon Aug 09, 2021 7:02 pm Yeah, I would be one of those "blue in the face" guys, I'm sure.

So to apply your kind explanation to that wiring schematic, the only way to tell if a wire should have current is to track backwards (technically forwards). For instance, on that diagram, there is a red wire that goes from the battery positive to the main fuse. Then from the main fuse another red wire goes to the ignition switch and when the key is "on" current flows though the black wire to the fusebox (with the understanding that technically, the current flow starts at the green ground wire). When the switch is "off", the current just flows from the ground back to the battery via the red and green wires and/or does nothing.

Where I got so head pounding confused was that if you keep following that black wire it also goes to the regulator/rectifier which I mistakenly assumed was the source of the current to the fusebox. Instead, if I'm on the right track, the current to the fusebox does not rely on the rectifier/regulator at all. If I disconnect that black wire from the regulator/rectifier, as long as the battery has power and the key is turned on, the fusebox would have current, correct? The schematic would also imply that for whatever reason, the key has to be turned on and the rectifier/regulator have positive current on that black wire to function correctly, correct?

Anyway, I didn't mean to get into this so deep, but for me, this is eye-opening.
Yes, we look at these things from the easiest way to understand them and that starts at the positive battery post and work toward the load. Even though it’s all just the opposite. The current actually starts at the battery’s negative post and then through ground/frame/motor and then to the load of the circuit and then backwards through the relays, switches, etc..until it returns to the battery’s positive post. The battery terminals are named positive and negative due to the free electrons that are created by the chemical reaction in the battery. Almost all of them collect on the negative terminal internally and since their charge is negative, the terminal is negative. The positive post is named for being much less negative, positive in relation to the negative terminal because it has atoms that are short an electron making their charge positive. The black wire is the “ignition” wire that is required to turn on the regulator, if the power were to be missing there, the alternator wouldn’t charge the battery. When considering current flow, “Conventional” current flow is the name we give the current flow that makes it easier to understand. + to -
Blueten99
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Re: Starts and runs but no headlight or instrument lights

Post by Blueten99 »

I got the replacement fuse box in and it works - problem solved!
Your explanations are spot on. The atomic level references are icing on the cake. I always had it backwards in my head regarding atoms. It's counter intuitive to think of atoms that have fewer electrons are positive but it makes sense, current would flow towards those atom thus it's the "positive side". I will study more.
Sir, you are a blessing and appreciated. Thank you.
Techdude2000
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Re: Starts and runs but no headlight or instrument lights

Post by Techdude2000 »

Blueten99 wrote: Mon Aug 23, 2021 6:52 pm I got the replacement fuse box in and it works - problem solved!
Your explanations are spot on. The atomic level references are icing on the cake. I always had it backwards in my head regarding atoms. It's counter intuitive to think of atoms that have fewer electrons are positive but it makes sense, current would flow towards those atom thus it's the "positive side". I will study more.
Sir, you are a blessing and appreciated. Thank you.
Excellent! Glad to help and glad she’s running good again. Now go ride it like you stole it! :D
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Re: Starts and runs but no headlight or instrument lights

Post by WingAdmin »

The reason the electricity flows what we might consider to be "backwards" is because the concept of positive/negative terminals and current flow was established BEFORE we actually knew what was actually going on, that it was electrons, and that electrons contained a negative charge. By the time this was discovered, the standard had already been in place for years.

You can read about the history on this page: https://www.douglaskrantz.com/ElecElectricalFlow.html


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