dragonnoodle Posted September 5, 2007 Share Posted September 5, 2007 I was told the bike was a 79 so I was looking at those wireing diagrams, Haynes, and most of the wires didn't match so I checked the 78, since a 79 xs400 doesn't exist on some part site, almost everything matched the '78 diagram. Low and behold everything matched until I got to the ignition switch 78 4 wires 79 3 wires I got three on both sides of the junction plug not spliced or anything. My question all my lights work; turn signal front and back, brake light running and front and back brake switchs 12volts. Head light ~.5 volts and gauge lights ~.5 volts. How does the bike run and all the electrics work with full power and the head light and gauge lights only get .5 volts. I can understand no power but just a little bit of power.. I'm stumped. Thanks for all the help, Scott Link to comment Share on other sites More sharing options...
Guest Brian Bonner Posted September 5, 2007 Share Posted September 5, 2007 I was told the bike was a 79 so I was looking at those wireing diagrams, Haynes, and most of the wires didn't match so I checked the 78, since a 79 xs400 doesn't exist on some part site, almost everything matched the '78 diagram. Low and behold everything matched until I got to the ignition switch 78 4 wires 79 3 wires I got three on both sides of the junction plug not spliced or anything. My question all my lights work; turn signal front and back, brake light running and front and back brake switchs 12volts. Head light ~.5 volts and gauge lights ~.5 volts. How does the bike run and all the electrics work with full power and the head light and gauge lights only get .5 volts. I can understand no power but just a little bit of power.. I'm stumped. Thanks for all the help, Scott I've got the same problem but oddly only with the headlight. I've got an '80 xs400sg, and the wiring diagrams all suck in one respect, they don't show what happens within the relay. I kind of suspect that somethings wrong with the relay in my case. Maybe you've got the same problem? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted September 5, 2007 Moderator Share Posted September 5, 2007 I've got the same problem but oddly only with the headlight. I've got an '80 xs400sg, and the wiring diagrams all suck in one respect, they don't show what happens within the relay. I kind of suspect that somethings wrong with the relay in my case. Maybe you've got the same problem? UK bikes don't have relays. the 4th wire feeds the main beam pass switch. I had to solder an extra wire from the ignition switch live to the pass switch on the left side and back to the headlamp main beam. Link to comment Share on other sites More sharing options...
dragonnoodle Posted September 5, 2007 Author Share Posted September 5, 2007 When you say relay do mean the ignition itself or the connectors? Drewpy you just added a wire from the ignition to your head light switch? Did you have any issues with that? Link to comment Share on other sites More sharing options...
Cy Welch Posted September 9, 2007 Share Posted September 9, 2007 I've got the same problem but oddly only with the headlight. I've got an '80 xs400sg, and the wiring diagrams all suck in one respect, they don't show what happens within the relay. I kind of suspect that somethings wrong with the relay in my case. Maybe you've got the same problem? The headlight relay is a simple latching relay (has an internal diode that locks it into the on position until voltage is removed once it's been energized by a voltage pulse from the diode in the wiring harness off the stator. You can test if it's the problem by unplugging the relay and and putting a jumper across the connection (at the bottom I believe, but it might be the top two, just try one then the other, if you do them that way with the engine off there will be no problem), if it's the relay then the headlight will come on when you put the jumper on. I ran mine with a jumper for a couple of years because I didn't have the relay. You can open the relay and clean the contacts if that is the problem, as it's a mechanical unit. However, there seem to be plenty of them on ebay for a reasonable price if the relay is the problem. Also check the headlight fuse connections as those are notorious being poor (corrosion and such). I replaced my fuse box with an aftermarket unit made for off-road vehicles that uses the modern blade type fuses. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted September 10, 2007 Moderator Share Posted September 10, 2007 When you say relay do mean the ignition itself or the connectors? Drewpy you just added a wire from the ignition to your head light switch? Did you have any issues with that? not really, the wire from the switch was already there, being part of the left switch loom. I just had to buy some japanese type bullets and solder tup o the ignition switch by copying the old one I had. Link to comment Share on other sites More sharing options...
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