Question'77 Yamaha XS750 2D - a Triple. Both when it is running or just
in "on" position, the turn signals will light up (new bulbs), but
will not flash. I've replaced flasher 3 times (used units). I tried (2)
new auto flash units, and the signals would not even light up at
all. New battery, fully charged, tested good. I have sprayed
contact cleaner, checked connections, installed new negative
and positive battery cables, the ground strap on left side is
attached to airbox and frame. Headlight, brake light, horn and
starter all work. Fuses good.
Why don't they flash?
AnswerHi Chris,
I'd have to trace the circuit to learn what's causing the problem.
What's the condition of the turn signal switch and contacts?
Here's a link to the Yamaha Triples website and the text from the file I found there reference the turn signal problem. It's something to look into.
http://www.yamaha-triples.org/workshop/harnett-signals.asp
Respectfully,
Mark Shively
Bernie's lecture on Turn Signals
I feel a lecture coming on. So, class, sit up and pay attention. And for those of you who already know how the turn signals, or indicators work, go outside for a beer or a smoke.
> Paul
> Ps. The resistance in the turn signal shouldn't be a big factor the only
> thing using power is the bulbs.
The way the turn signals on your bike work is what is known as "Cheap and Nasty".
All the manufacturers do it this way. The resistance in the turn signal circuit is acutally very important to how they work, and so is the rating of the bulbs used.
When you set the indicator switch to turn, you make a contact in the handlebar switch, and this provides either power, or a ground to the indicator relay. This is usually a three terminal device located conveniently where you can't get at it.
The relay picks up, and this provides power through the relay coil to both front and rear indicator lamps. (Turn signals for the US residents.) The current drawn by the bulbs in the indicators heats up a bi-metal strip in the relay, and when it gets hot enough, it bends the moving relay contact that is providing power to the bulbs away from the fixed contact and the bulbs go out.
This bi-metal strip then cools down. It contracts and the moving contact makes the circuit with the fixed contact and the bulbs come on again. And so on. So the lights flash. And will continue to do so until you remove the power or gound from the input to the relay.
The rate of flash is the next problem.
The current able to be drawn through the indicator flasher relay is entirely dependant on how much resistance there is in the circuit. Too much, and the bi-metal strip won't heat up enough to bend. Not enough, and it will fuse and burn out.
A common problem is when one of the indicators has a blown bulb, the other one won't flash. This is because the bulbs are in parallel, which halves the resistance of one of them. With only one, there is twice the resistance to current flow, and so the relay won't flash. There isn't enough current being drawn.
With high resistance connections in the circuit, and the most common in my experience is the bulb holder is rusty or dirty, again there is too much resistance for the relay to heat up and so flash. Cleaning the holders and the bulbs reduces the resistance, and once again, there is flashing.
Using the wrong rating of bulb also causes problems. It is the resistance of the two filaments that is important. And different ratings of lamp will have different resistances. The tricky part is we are talking about the hot, or ON resistance. This can only be calculated because it is much different from the cold, or off resistance. Ohmmeters do not work well when there is 12volts across the device under test.
But it is a simple calculation. Rating of the bulb in watts = volts applied x current drawn. To rearrange, amps = watts divided by volts.
Read the rating in watts from the lamp body, and measure the voltage across the lamp. Divide one by the other. Easy.
One last thing. This is all complicated by Yamaha's miraculous self cancelling indicators. This is governed by a little black box living up under the tank. It has five wires coming out of it into a plastic terminal block. Two of them go to the speedometer, and three to the handlbar switches. It is a timing circuit, with a reset built in.
The trick is there are two auxiliary contacts in the handle bar switch. And if these get dirty, not only do you indicators not turn off automatically, but they won't turn on at all. To test if this is your problem, unplug the self cancelling unit at its connector, and if the little contacts in the handlebar switch is fault, the indicators will work again.
Substitue relays. Emgo make a perfectly acceptable flasher relay if yours is faulty. Same size can, same pattern connector. Fits straight in, works well. Just be sure to get the 12V version. Alternately, try one off a wrecked Japanese bike in a bone yard. They are nearly all Mitsubishi electrical ones, and are often interchangable. One of our Kawasakis is using a Honda relay.
So there it is. Just remember, resistance IS important when dealing with indicators on your bike.
Bernie.
