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Turn Signal Relay Repair

Flasher Relay Repair

by Steve DeForest
June 2001

Hi, 1986 K 100 RS.

The other day I had the turn signal fuse pop on me. I removed the tank and inspected the wiring harness for chafing and other obvious defects. Then I installed a new fuse.

Now the left side turn signals were on, including the dash light, but none were blinking. Neither would it cancel and turn off.

So I got out my trusty Haynes manual and found the schematic for my bike. I found that unlike cars where the flasher unit is the last thing before ground electrically, these bikes put the flasher unit immediately after the fuse.

I originally suspected a bad switch, which is a possibility, but when you combine that with no flash, I decided to check the flasher unit first.

The flasher is about 1″ by 2.5″ by 2″. On my bike it is mounted to the back wall of the electrics box. I dismounted it and unplugged it.

Looking at the bottom of the flasher you will notice a single tab on each side. This would lead you to believe that the plastic cover would be removable. You would be correct.

Upon removing the cover, you will notice there are many resistors and transistors and two conspicuous relays. These relays are what causes the turn signals to blink.

The points on one relay had arced and stuck shut. I pulled the contacts apart with a small screwdriver and sprayed some contact cleaner on the contacts. Then I reassembled the relay installed it on the bike and tried the blinkers.

The system now works as advertised.

If this info would be of help to someone out there, feel free to edit it and post it on the site. Happy motoring and keep the rubber side down!

Steve DeForest

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