The bike was running fine, but when I got home and turned it off to get the garage key it wouldn't start. I have diagnosed the problem to a short on the wire from the start button to the solenoid, as it has a floating voltage of up to 2V when it is disconnected from the solenoid! When the start button is pressed there is 12V at the switch end, but no change at the solenoid end! As the wiring diagram shows this as a single wire with no other connections, I am stumped as to where it is shorting. The bike has what I assume is an after market alarm that has since been disabled when a previous owner lost the dongle for it, so there may be a connection from the start wire to the alarm and a fault here. Has anyone come across anything like this before? I also found a really odd connection from the indicator relay to the front indicators, where someone had just soldered a new wire to the one coming out of the relay and I have no idea why anyone would do this either, so assume it's another alarm oddity.
There’s a little white plug in the back of the solenoid that often comes loose. Make sure it’s plugged in properly and wrap a tie wrap around it to stop it falling out.
The floating voltage is with the plug removed. The 12V from the switch doesn't even get to the plug, as this was where I was measuring it.
Did you test for 12V across the plug or are you testing between the plug + and a separate earth? If you check it to a separate earth and you're still getting FA then the fault is in the wire between the starter switch and the white plug, if you get 12V it means the fault is with the earth wire from the white plug. Won't fix it all but helps narrow it down.
The wire from the handlebar switch to the solenoid does go through a big multiplug, possibly an issue with connections there?
I think they may have used the original indicator feed to connect to the alarm and then added the new wire to replace the one they used, but I am guessing.
I'm testing from the plug to the battery negative terminal. There is 12V to the switch and 12V out of the switch when it is pressed, measured at the switch itself, and 2V at the plug. With the switch not pressed there is a floating voltage on the wire at the switch and the plug, hence I think it is the 12V wire and not the earth wire. Thanks.
Good luck with the fault finding, definitely sounds like the feed to the solenoid. Fingers crossed for an easy fix!
You've just given me an idea. I've found the multiplug, so I'll disconnect it at the weekend and check the voltage and resistance from the switch to the multiplug. As it's disconnected it should be 0V and very low ohms. If the short is in this end, it won't show up with the plug disconnected, as there's no input voltage to this part of the bike, so I'll test the other piece of the multiplug to the solenoid plug. If the short is in this part, it should be present, but if it has vanished, the short will be in the cable behind the headlights. Yay, this should tell me which part of the bike the short is, after which I can take it to pieces and trace the cable.
When you split the multiplug, check for verdigris inside which could be both the reason for the lack of continuity and the floating voltage - dis or VHR on the starter feed and a resistance / partial short through the corrosion to another wire at a guess. Good luck!
