Yamaha's Auto Cancelling
Turn Signals
how they work, how to fix them
Blaine Hoopes 8/29/99
I recently restored an '81 XS650 and the turn signals would not cancel automatically like they are supposed to. I immediately suspected the little black box that is the cancelling unit. Having several other '81-'81 Yamaha's to test with I tried the suspect unit on another bike and it worked perfectly. Next I pulled the speedo out of it's cover and found the sensor was not in place as it should be. It is a black plastic piece with two wires attached and pops into a slot just below the speedo lightbulb. The sensor is a magnetic reed switch that closes when a magnetic field comes close to it. The speedo works by spinning a round magnet inside a cup attached to the speedo needle and the turn signal sensor sits close to this magnet and switches on/off as the magnet rotates telling the turn signals that the bike has traveled so much distance. After repositioning the sensor and having it still not work I looked closer and saw that the reed switch was broken. The reed switch is sealed inside a glass tube with an inert gas so the contacts never corrode or get dirty. I found a new reed switch at an electronics shop for about $1.50 and soldered it back in place, assembled the speedo and still my signals would not cancel.
The whole history of repairing this bike had been one of finding odd problems where every possible part had already been replaced by someone (usually incorrectly) except for the actual failed part. I decided the sensor being out of place and broken only indicated that someone had already tried their best to fix the problem and broken it in the process.
I observed that all of my other Yamaha's will cancel the turn signal when the key is turned off and back on again. This particular one did not do that, turn the key off and back on and the signals started flashing again -- aha, a clue! I took the switch apart and saw how it works. A slider switch connects left or right signal and stays slid to whichever side you last selected. Only when you push the turn signal button in does it re-center the slider. There is a copper plate under the selector lever with copper leaves on either side of the inner part of the lever. Looking at a good switch I saw that these leaves do NOT contact the lever except for while the lever is pushed fully left or right - on the malfunctioning bike these copper leaves were touching the lever all the time. It turns out this copper piece is a switch to allow you to start the turn signals working the same direction again even after the canceller has stopped them. With the copper leaves touching all the time the canceller thought I was holding the lever in left or right position and so it kept the signals flashing. I simply bent them out a bit to the proper location (so the lever just touches them when pushed fully left or right) and finally everything works perfectly.