For owners who have swapped all incandescent turn signal bulbs out for LED bulbs, the turn signal indicator on the dash does not blink. It stays constant for as long as the turn signal switch is on. This despite the actual turn signals blinking correctly, and an LED Turn Signal Relay being installed.
Note: While this DIY was made based on the 2015 Kawasaki Ninja 300 ABS motorcycle, it should apply to most modern vehicles which exhibit this issue, with the only variation being the value of the resistor used.
Difficulty: 2 out of 5
Tool Requirements: 2 out of 5
Time: 2 hours
After installing LED turn signals on both the front and rear of my Ninja 300, the LED turn signal indicator on the dash stopped blinking. That is, the turn signals would blink appropriately, but the indicator on the dash would stay steady.
As such, it is much less salient and you are much less likely to notice that you haven't turned them off after making a turn. It's extremely annoying after a while for such a small issue. With some bulbs this may happen (even if they are all LED's) and with some it might not. It doesn't seem to be simply dependent on LED current consumption, since it will still happen even if high power LED's are used on all turn signal lights. It's more dependent on the turn signal bulb design in particular.
Apparently the LED bulb which serves as the turn signal indicator inside the dash operates a bit differently to the turn signals, and isn't simply wired in series or parallel. That's why the turn signals can flash while the dash indicator stays constant. I've seen some not totally convincing arguments for this, but the end result is that the dash indicator apparently is looking for some sort of resistive load which the LED's are not satisfying.
One size fit's most solution:
If you want to find the exact value of the resistor needed for your application in particular
Other typical electrical tools will be needed:
The solution is simple, however it is hard to find the correct component advertised as such online. The typical product is the big "Turn signal load resistor" in obscene wattages and amperages totally unsuitable for our bikes, much more expensive, and 10 to 50 times bigger than it has to be.
In other words, DO NOT use the 10-50w Turn Signal Resistors advertised online. It is not the right solution for this problem.
The correct solution is to use the properly sized 1w resistor, once we find out what that proper size (read resistance) is.
The easy way to solve this is to buy a couple of "220 Ohm 1w resistor" and install in parallel with the turn signal bulb on both sides of the turn signal circuit. Only one resistor per side (Left and Right; not per bulb). That is the simple answer and should solve the needs of 99% of the people with this issue*. For people who appreciate the "Right" way or want the exact value, read the following steps.
*That was the case with this 2015 Kawasaki Ninja 300. Given that most motorcycles use the same size 5w bulb, it should work for most people with this issue regardless of the brand. Nonetheless, your mileage may vary.
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If you want a more exhaustive answer, see the next step.
The exact values that can or should be used may vary. In order to select the resistor, you want to select the largest one Ohms-wise you can get away with. This is because all the resistor is doing is putting an extra resistive load on the turn signal circuit, and converting that consumed load into heat.
The Turn Signal Load Resistors you will find advertised as such are typically around 6 or 10 Ohm resistors, in wattages that are normally in the 10-50 Watt range. When installed, these resistors consume around 32 watts or 2.3 Amps (a lot) and get hot as hell. I initially tried one, and within seconds I don't doubt it would have melted plastic on contact. That is wholly unsuitable for a 12v circuit! The resistors consume much more than the LED turn signals would (or even the incandescent bulbs they replace for that matter!), and waste all that electricity turning it into heat. This is completely undesirable in small motorbikes with small batteries and mediocre charging systems. The actual resistor needed consumes about 0.72w and 0.05 Amps. That's 4600% less current draw! A brutal difference. While the automotive load resistors are the size of a 9v battery, the suitable 1w resistor is more like a bloated grain of rice and can be installed right alongside the wiring which leads to the turn signal bulb itself. They get uncomfortably hot to the touch after a while, but little hotter than that.
The Ohm rating determines how many "amps" the resistor consumes (how much it wastes as heat). If the ohms are too small, it get's closer to representing a short circuit and the amps consumed rise (less ohms, less resistance to current flow, higher current flowing). This is "bad", since it's wasted electricity. You want the largest Ohm value (aka lowest current draw) that still makes the dash indicator blink strongly instead of either staying on constantly or fading on and off as if it were an incandescent bulb. 220 or 270 Ohm is the value I found suitable.
The Wattage rating represents how much of a load the resistor can put up with, or in other words how much heat the resistor can dissipate without burning up. This value is selected after the ohms are selected. You simply choose the next value up.
That's how you choose a load resistor's specs.
Example: If your resistor consumes .72w (you calculate this knowing the voltage of the circuit and the resistance of the resistor), you choose the 1 Watt resistor. If it consumes 0.4w, you buy the 1/2 Watt resistor. There is no disadvantage to selecting a larger Watt rating, besides a bigger and more expensive resistor. One factor to take into account is that the turn signals have a 50% duty cycle (half the time on, half the time off), so in theory you could get away with half the wattage. But in practice it isn't worth it, and the extra wattage is a margin of safety that compensates for the insulation around the resistor which protects it (like heat shrink tubing, electrical tape, etc).
If anyone wants to know (or for my future reference in the future) how to calculate the load resistor, the best and quickest way is actually to do it is in practice. Since the method the dash indicator works by is known only to Kawasaki, this is the best option. To do this, purchase a variable resistor with a 1-500 Ohm Range (a 1-1000ohm potentiometer would provide some extra margin at the expense of unneeded precision but can be a better choice in some cases) with a wattage rating of anywhere from 1 to 5 watts or greater. Since I didn't know what to expect I used a huge 100w variable resistor. It was an utterly oversized, but perfectly suitable, choice.
To test, remove some of the insulation from both positive and negative wires on the lead which connects to the front turn signal bulb housings. Connect a separate alligator clip lead to both wires, and connect those leads to the variable resistor (putting the variable resistor in parallel with the turn signal bulb). The variable resistor should have 3 connections. Between the two farthest connection the resistance will always be the maximum resistance of the resistor. Between one end and and the middle connection the resistor will be the value dictated by the knob. Connect one cable to one end, and another cable to the middle connection. Resistors are not polarized so it doesn't matter which cable connects where. The only precaution is to not connect both leads coming from the turn signal cable since that would be a short circuit and would blow the (replaceable) fuse. Also, never turn the knob to 0 Ohms since that would also be a short circuit and also would blow the fuse. Neither should create permanent damage, just the hassle of changing a fuse, but it isn't worth the risk.
Start with the value of the variable resistor at the largest value possible (1000 Ohm for a 1000 Ohm variable resistor). This will be the closest value to an "open circuit", and will have the least amount of current draw. Turn on the bike and turn on the turn signals for the side the variable resistor is connected to. With the variable resistor at the largest value, the dash indicator should stay constant and nothing should be different (since it doesn't consume enough current). Slowly turn the variable resistors knob in the direction of lower resistance. At some point, the dash indicator bulb will start flashing slowly and fading off and on (as if it were an incandescent bulb). Keep turning the knob until the dash indicator bulb sharply flashes on and off with no fading. This is the correct value of the resistor you need. Once you have found a position of the knob you are satisfied with, turn off the turn signals and disconnect the variable resistor. With a multimeter, read the value of the resistance of the variable resistor between the connections you connected to the turn signal circuit. In my case, the value at which the dash indicator light started fading on and off was around 330 Ohm. At 300 Ohm the dash indicator light was flashing strongly with no fading. As a margin of safety, I selected the next lower available resistance: 270 Ohms. 220 Ohms would be a safer choice, at the expense of a higher current load and more wasted electricity as heat, but is still a sound choice. Not all values of resistors are available. Typical values in this range are: 1,10, 22, 47, 100, 150, 220, 270, 330, 470, 510 Ohms... .
Of note is that the value of the resistor oddly enough does not vary with or without the turn signal bulbs connected, nor is it possible (at least with LED bulbs) to make the dash indicator work like a "Turn Signal Error Indicator". By this I mean that it isn't possible to make the dash indicator blink if both turn signals work, but stay constant if either the front or the rear bulb is defective (if one bulb fails, only "half" the current is drawn by the bulbs which can be detected - This is why car turn signals flash quickly if a single bulb is defective). If the minimum value found to make the dash indicator work is 270 Ohm, the minimum value is still 270 ohm regardless of one or both bulbs being defective. With incandescent bulbs I believe that if one of the two turn signal bulbs (front or back) goes bad, the dash turn signal indicator stays constant in order to alert the rider.
Once the value in Ohms of the resistor is chosen go to a Watts / Volts / Amps / Ohms calculator online and input the value of Voltage (14v) and Resistance (Whatever value you were satisfied with). The calculator will return Wattage and Current. The value of the current is how much electricity is wasted as heat, and the value of wattage is the minimum watt rating the resistor you choose needs to be in order to not burn up. For 14v and 270 Ohms, the current is 0.0518 Amps and the wattage is 0.7259 Watts.
Purchase the resistor and simply place it in parallel with the turn signal bulb. By parallel I mean bridge both positive and negative turn signal cables via the resistor. Wrap carefully (but not excessively) to avoid short circuits. Only one resistor is needed per side (NOT per bulb). I found the best place to be the lead which is installed on the side fairings where the front turn signals are located, simply installed inline with the cable and heat-shrinked around it. You can barely tell it's there.
So there you go, that's the proper solution to this issue I had, that no one else seemed to have, and for which there wasn't any information online.
These notes are mostly for my own reference in the future.
Current draw as measured at the fuse under the following circumstances:
Observation: LED's draw very little current, and something is drawing current regardless of bulbs. Perhaps there is an error of measurement since these values were copied on a napkin months ago when I took on the issue.
Resistance to make dash turn signal indicator bulb blink properly:
Observation: There is no value of the resistor for which the dash indicator will blink when both bulbs work properly, and stay steady when one of the two bulbs is defective.