GL1200 Electrical System - Connecting to the System

Information and questions on GL1200 Goldwings (1984-1987)
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Joined: Wed Nov 18, 2015 12:44 pm
Location: Victoria, British Columbia, Canada
Motorcycle: 1985 GL1200 LTD, 2008 GL1800

GL1200 Electrical System - Connecting to the System

Post by Rednaxs60 » Sat Dec 02, 2017 8:34 pm

Connecting new/additional loads, or aftermarket replacement components to the GW electrical system.

Previous electrical threads:

Power Junction: viewtopic.php?f=5&t=40650
GL1200 Electrical System: viewtopic.php?f=19&t=40770
1985 GL1200 Rectifier Testing: viewtopic.php?f=12&t=40801

There is a lot of information and discussion regarding this subject. There are as many recommendations on how to do this as well, and I expect some interesting discussion may ensue. The information provided is not to influence or change how someone else manages and maintains their bike's electrical system., but is presented as my understanding of the topic, and how I will undertake any electrical system changes to my '85 LTD.

I must caveat the following with an admission that I too have not always adhered to a best practice regime. I do; however, continue to look for a better understanding of what I am working on and when I find what appears to be a better way ahead that is based on sound information and logic, I try to include this new information into what I do.

I have also had real life experience with some of what I write, and sometimes the added expense associated with my decision(s) could have been avoided.

I have been researching how the electrical system is designed and works on my '85 LTD. I have come to an understanding of the electrical system on my '85 LTD and expect this to be common with the other GW models.

There will be some exceptions such as the 1500/1800 that have external alternators. How these alternators are designed and compared to an automotive alternator, and how these are connected into the respective electrical systems is anther subject.

Back to the older GWs such as my bike.

First tenet that I use is that the electrical system on the GW is designed the same as that of a car, and that the GW is a car on two wheels with everything crammed into a very small space.

I have browsed, read, researched the internet, and various forums to gain an understanding of electrical system design and concepts with regards to the various design components. This was expanded to include the addition of new components/loads to the electrical system, and aftermarket replacement components.

There has been one key element that is common between the motorcycle and automotive industry. The key element that is common between the two industries is the use of a junction, sometimes called a power junction, that distributes the electrical system power to various components. This is to be expected because the motorcycle industry is based on the automotive industry for a lot of design aspects.

This junction is where the alternator output connects to the vehicles electrical system. It is where the alternator output current is distributed to the various loads. I mention current at this point because another tenet that I observe is that the electrical system voltage is maintained at 14.2 VDC by the regulator, even though it will fluctuate but return to 14.2 VDC, depending on the various loads being applied/removed from the electrical system.

Another reason for this is that alternators are expected to maintain this mean electrical system voltage of 14.2 VDC (give or take a point or two) regardless of amperage output size. Discussion regarding alternators never revolves around voltage, but around amperage rating.

Having mentioned the above, I have looked at a number of motorcycle and automotive schematics, and have found this common element, I will call it a power junction, where the alternator current output is sent to all the loads, to be consistent. There is generally two wiring branches, one to the ignition switch and one to the battery. In reviewing electrical system schematics, you will notice that all loads (there are a few exceptions – not many) are after the ignition switch, or controlled by the ignition switch. The only primary exception is the battery.

The battery is used to start the bike, load levelling – voltage spike absorption, and supplemental power should the charging system not produce sufficient power for the electrical system operation. The industry mean voltage of 14.2 VDC is considered the optimal voltage to operate the vehicle electrical system and keep the battery fully charged.

At start, a battery in good condition is discharged approximately 3% of state of charge. Once the vehicle is started, the battery is quickly charged back to a 100% state of charge. The mean electrical system mean voltage of 14.2 VDC is forced into the battery at a high current rate. The battery accepts the charge until it gets back to or close to 100% state of charge, after which it starts to resist the current flow (in actuality the battery starts to resist the influx of power as soon as it starts), reducing the charging rate (amperes) until it gets to a point that results in a trickle charge to the battery. At this stage there is very little current flow to the battery.

As mentioned before, all loads are after the ignition switch. There are no additional loads connected to the wire going from the power junction to the battery, good design and works well.

Here are a few schematics to illustrate what I have mentioned above.

GL1200 LTD Schematic

In the GL1200 LTD schematic, there are no additional loads on the battery, all loads are after the ignition switch. This schematic shows one exception to the no additional loads on the battery side of the electrical system; however, the electrical system was designed this way, and my premise presented in this article is still sound.

Automotive Electrical System

In the automotive electrical system schematic, you will notice that a junction block, a power junction, is used to distribute the output from the alternator. It also shows that the sense wire to the regulator is joined at the junction block as well.

Automotive Electrical Schematic 2

In the above schematic, a junction block, power junction, is used to distribute the output from the alternator.

GL1200 Electrical Schematic

The GL1200 electrical schematic above also has a power junction where the alternator output is distributed to the electrical system.

In all the above schematics, there is a power junction to distribute the alternator output to the electrical system. Even though the battery is an essential element in the operation of the electrical system and bike operation, that when it comes to power distribution, the battery is considered only as a load on the system that we know requires varying degrees of current input. The automotive schematics provide a simplistic representation of the electrical system; however, the follow on schematic details regarding electrical loads would be after the ignition switch.

Enter the human factor. This is where the design intent of the OEM meets us, and then all bets are off.

As our bikes have aged, replacement parts from the OEM have been discontinued, and aftermarket components have been developed, we have had to adapt to the changing landscape. There have been technological improvements that have us upgrading various components for better performance and reliability.

I would like to discuss aftermarket components that are intended to be direct replacements for OEM components.

One of these is the replacement of the OEM shunt type regulators. These degrade over time, and do fail. This type of regulator is very inefficient, but technology has improved and surpassed this shunt type regulator. Enter the series type regulator that uses the latest technologies.

With these new series regulators being used to replace the original OEM shunt type regulators, there is generally a difference in the number of wires from the regulator to the electrical system. This in itself is not an issue; however, it becomes an issue when the aftermarket manufacturer/distributor recommends connecting its unit to the electrical system that is not the same as for the unit that is being replaced.

Manufacturer/distributor installation instructions should be such that you can install the new unit using the existing wiring from the unit being replaced. There may be some modification to the OEM wiring connection, but this should be explained in the installation instructions, complete with how to make the changes. Installation instructions that do not do this, but recommend installation by bypassing/circumventing the original system wiring design for ease of installation is not a best practice scenario.

I understand the reasoning/rationale that has been the impetus for certain practices to become a matter of rote over the years. I submit that even though this approach will work, it may not always be a best practice scenario.

Not adhering to the original design of the electrical system can be problematic, and the system operation may be impacted and not in the best sense. As the owner/operator, you will probably question the change from the previous installation, and may or may not get an answer that fits your specific situation.

Another area of interest regarding this issue is the external alternator modification to replace the internal engine alternator stator, commonly called the “Poorboy” conversion.

Again, with the alternator conversion there is a lot of information on how to install the various components, but very little on alternator selection and how to connect the alternator into the bike's electrical system.

I have installed the alternator modification on my '85 LTD. Before I hooked the alternator into the electrical system, I removed the old charging system wiring, including the power junction. With the power junction removed, I installed a new wire from the starter solenoid to the ignition switch and commenced installation of the wiring to connect the new alternator up to the bike's electrical system.

Power junction Removed

When I removed the original charging system wiring, I did not have the same understanding of the electrical system as I do now, or understood how this affected the electrical system operation.

The alternator I selected for this modification was a 3-wire alternator, rated at 55 amps. It fit the operation profile and was small enough in size to be successfully hidden behind the lower left fairing without any modification(s) to the fairing. It is readily available at the local auto wrecker and very reasonably priced. I have since replaced the alternator first used with one from a 1988 Pontiac Firefly 1.0 litre turbo.

I have covered the different alternators that can be used for this modification in another thread. Suffice it to say, I would recommend a 3 wire alternator instead of a one or two wire alternator. Your requirements may differ and as such your choice of an alternator as well.

I installed the alternator output wire directly to the battery with a 50 amp circuit breaker in line. I connected a 12 VDC switched wire for excitation, a lamp wire for visual indication as to whether the alternator was working and the sense wire directly from the battery.

The charging system never worked quite as well as when the OEM system was installed. I submit that if the stator had not failed, I would not have an external alternator installed.

The integral dash voltmeter always indicated an electrical system voltage of some 05. to 0.7 VDC less than actual at the battery. The electrical system never seemed to adjust to voltage fluctuations as well as it should have, especially when the rad fan would come on. The electrical system voltage would drop, but not recover as one would expect.

Fast forward a year and a half, and armed with new knowledge of the electrical system, I decided to rewire the electrical system to replace the power junction that I removed.

Schematic for Rewire of '85 LTD

I used this schematic as the template for the install of the new power junction and associated wiring change(s).

I used a Blue Sea power bar and installed it where the OEM regulator used to be located. The connections at this power bar are:

1. Alternator output wire;
2. Alternator sense wire;
3. Wire to ignition switch;
4. Accessory fuse block power supply;
5. Battery Tender connection; and
6. Charging wire to battery.

After the rewire, trialled the new power junction installation. The results were very good, and mirrored the electrical system operation before I did the external alternator modification.

This new power junction gives me the flexibility of adding additional power bars (power junctions) if required, and expect the electrical system operation to operate as designed.

The in dash voltmeter indicated electrical system voltage that was the same as that seen at the battery with a voltmeter – 14.2 VDC. I have 2 sets of driving lights that can be switched on/off, as well as the rad fan. I switched on the driving lights and the system recovered as it should. The rad fan was turned on, and the system voltage dropped but recovered as well. The charging/electrical system is now operating as it should.

Had I not removed the old charging system wiring, I would have been able to connect the alternator output and sense wire to the red/white wire going to the power junction and starter solenoid. The original rectifier black wire would be used as the 12 VDC excitation, and the only other wiring would be the indicator lamp on the dash.

If you are using a one wire alternator, the alternator output wire connects to the red/white wire going to the power junction and starter solenoid.

If you use a two wire alternator, the alternator output wire connects to the red/white wire going to the power junction and starter solenoid, and the original regulator black wire is used as the 12 VDC excitation to the alternator.

The last section of this article will deal with adding new/additional electrical loads to the bike's electrical system.

The accepted practice by most is to use the battery as a load/connection centre. There are aftermarket products such as accessory fuse blocks that are designed to attach to the battery terminal(s) to provide expansion possibilities for you, the owner. It is also the sentiment of many that this is the best way ahead. I have mentioned above and in my other threads that this is not always a best practice scenario.

The schematics I have included in this article clearly illustrate that the OEM design considerations are such that connecting new/additional loads at the battery terminals is not a best practice scenario as there are none. In researching this issue, the automotive industry, specifically in the vintage and early model car restoration sites, recommends installing or expanding on power junctions for new electrical loads instead of using the battery as a connection/load centre.

Having mentioned this, I would recommend that to add new loads to your bike's electrical system be be undertaken such that the connection is on the upstream side of the power junction (ignition switch side). This can be accomplished by connecting a new wire splice at or near the power junction. You can also install a new power junction, with the associated rewire.

There are many ways to accomplish what you want to do, but I again submit, that installing new loads correctly, and from the correct location in the electrical system wiring, will ensure continued correct electrical system operation.

To summarize:

1. Our older GWs have a power junction that is a key element in the correct operation of the electrical system;
2. Aftermarket replacement unit(s) should be installed the same as the OEM unit(s) being replaced;
3. DIY modifications should be installed the same as the OEM units that it is replacing; and
4. Connecting new loads to the electrical system should be at the correct location in the electrical system wiring harness.

I trust you have had a good read. It is a long post. The opinions expressed herein are mine based on my research and real life experiences. As I mentioned previously, I am not trying to convert or change how you work on and/or maintain the electrical system on your bike, but to present information as I have come to understand it.


"When you write the story of your life, don't let anyone else hold the pen"


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