Rear turn signal / marker lights ?

Further to Ken J’s thoughts on a wiring mod to allow the rear turn signals to also function as marker lights. Since the front turn signals also function as marker lights there must be something here which allows that to happen without negatively effecting the dash indicators. How can we determine how that works? Both the front and rear signals are fed by Lb and O wires —yet the front serves as both marker & turn lights. But there doesn’t seem to be any type of diode to stop cross feed —on this later wiring diagram.

Here is a view of the Combination Meter circuit from an ‘07 and later non-ABS model. Note that it doesn’t show the diodes and transistor which appear on Ken’s ‘02 - ‘07 wire harness.




And here is the rear lights cluster. Since the license light is ON all the time I wonder if diodes could be used to jump the Bl/Br of the license light to the Lb and O of the rear turn signal lights?

Or possibly jump the O, Lb and Bl/Br wires at the light cluster and add a diodes at the 9-pin connector for that light cluster to stop back feed to the CM?


Mind you this is all speculation on my part because I have no idea what I’m talking about.

Looking at the 2002 manual, this is going to be my tap point. It's a matter of finding that point in the wire harness. We all ready know that removing the orange and light blue wires at the dash connector will not work because power comes up those wires from the turn signal switch to activate the dash indicators. We tried that and found losing the dash indicators is not an acceptable trade off. If we look at the wire diagram we see that the new selected point goes directly to the rear turn signals with no other tap points.

Circled in red are the new points I am going to try. Unfortunately I believe I will have to cut those wires to separate them then splice them into the front turn signals right and left respectively. A risk I am willing to take on my Silverwing. It's a matter of hunting the wire harness inch by inch to find those points. When I had the Silverwing front opened, I did take notice to the harness going to the rear. The tap points will be under the front clip of the bike. I am sure of that.

As a test, I'm going to remove the rear 1156 turn signal lamps and do a temp install of two generic 1156 lamp holders and splice them in to the front turn signals and see the reaction. I'm going to be looking for any adverse reactions including additional current to the ballast resistors. Tracing out my extra dash panel, I found that the transistor noted in the turn signal circuit acts as an amplifier increasing the voltage for the turn flash. The ballast resistors actually slightly dropping the voltage of the marker lights to around 11 volts while the amplification peaks at around 13 volts giving a 2 volt differential between marker and turn flash. We must make sure the ballast resistors can handle the extra load along with the traces on the circuit board they are soldered to. Circuit board current is governed by the width of the trace and tolerances are very close by design.

Noted on the wire diagram is the actual lamp size and wattage recommended by Honda. 12 volts at 21 watts. For our readers information that lamp is actually a 7506 lamp. When we look at the lamp to change it, because the size is so close to an 1156 lamp, we naturally assume it is an 1156 lamp. An 1156 lamp is 26.9 watts. Those of us who do assume and purchase the 1156 for the turn signals are actually overdrawing some current from the ballast resistors. In my testing I will be using both the original 7506 lamps and the 1156 lamps to measure current flow across the traces of the circuit board and ballast resistors. Using 7506 lamps we should see 42 watts or 3.81 amps across the resistors normally. Boosting up to 4 lamps, we jump to 84 watts or  7.63 amps. Using 1156 lamps our normal draw 53.8 watts or 4.89 amps while boosting up to 4 lamps, we will see a draw of 107.6 watts or 9.78 amps. Can the traces and resistors handle the extra load? That is the question that needs to be answered before we proceed. Also note that we are working with a 10 amp circuit. If the circuit is possible and the sizes of the ballast resistors and traces are acceptable we must remember that for safety reason we should only draw a maximum of 80% of the fuse size of 10 amps or 8 amps respectively on the circuit continuously. That means we should be using the original 7506 lamps with a draw of 7.63 amps because we fall below our 80%. We may also want to think about an 1141 lamp that is 18 watts if we find the 7506 draws too much current across the ballast resistors and traces. Something to think about. This may also be a way to open the door to LEDs and ballast loading.


I guess once an electrical engineer who taught college will always be an electrical engineer who teaches. However being retired and board out of my mind from not working, I'm currently working as an electrical engineer in the automotive industry. I guess the brain never shuts down.

Above are pictures of the dash circuit board. What we are looking at are components of the turn signal/marker light circuit including transistor, relay, ballast resistors diodes, and other components. Someone put a lot of thought into the circuit when designing it. Looking at the ballast resistors, they are of the ceramic type at .1 ohms each. They are wired in parallel giving us a value of .05 ohms. This gives us approximately 1.2 volts loss for the marker lights or 10.8 volts nom. the voltage will vary with input voltage coming from the system. Inside the relay is an integrated circuit designed for timing and switching the relay.  We also have several diodes used for blocking voltages along with a wire wound resistor. There are also several other components in the circuit which aid in splitting the system between marker and turn signals. I have measured the circuit traces and found they are 4 mills thick. A fairly robust thickness for a PCB board. The narrowest part of the traces in question gave me an area calculation that will carry 6.8 amps at 12 volts. Not quite enough to run four 7506 lamps. However doable using 1141 lamps running 18 watts each. We may be able to live with that 3 watt reduction per lamp because we have a good lumen (brightness) value in the 1141 lamp.

The main reason I am doing all this before starting to cut and splice is because I want it to work for years as a permanent modification. There are so many times that a person will make a modification to something that will work several weeks to several months only to finally fail costing someone a huge amount of cash to repair because the mod over taxes the system slightly causing things to go south slowly. Then wham, you have a major problem. I've seen it happen too many times when people get an idea. In this case because the turn signal marker system runs through the dash PCB board, passing too much current through the traces of the board or its components if not rated to carry that amperage can cause a failure on the board causing someone to spend big money replacing it. Honda charges $850 for that board new and can be purchased used on EBay for about $200 if you get lucky. We don't want a PCB board failure. End of story.

Cosmic_Jumper wrote:

Further to Ken J’s thoughts on a wiring mod to allow the rear turn signals to also function as marker lights. Since the front turn signals also function as marker lights there must be something here which allows that to happen without negatively effecting the dash indicators. How can we determine how that works? Both the front and rear signals are fed by Lb and O wires —yet the front serves as both marker & turn lights. But there doesn’t seem to be any type of diode to stop cross feed —on this later wiring diagram.

Here is a view of the Combination Meter circuit from an ‘07 and later non-ABS model. Note that it doesn’t show the diodes and transistor which appear on Ken’s ‘02 - ‘07 wire harness.




And here is the rear lights cluster. Since the license light is ON all the time I wonder if diodes could be used to jump the Bl/Br of the license light to the Lb and O of the rear turn signal lights?

Or possibly jump the O, Lb and Bl/Br wires at the light cluster and add a diodes at the 9-pin connector for that light cluster to stop back feed to the CM?


Mind you this is all speculation on my part because I have no idea what I’m talking about.

From what I can see on your wire diagrams the mod should be the same provided the values on the PCB itself have not changed. The one thing I have noticed when I disassembled my original board for repair is that there was a marked space for the ABS warning LED as if it was ready to install. So maybe there have been no updates to the PCB from beginning to end of the run of Silverwings and ABS was planned from the beginning as an option.