desperately need HELP w HEADLIGHT PROBLEM!!!!

[iamdutchmaster]

after putting my bike back together, i noticed that the headlight would not come on while all the other lights were fine.... i replaced the bulb, checked the fuse and all the connections and everything seems fine... now heres the wierd part ... (with the ignition on) when i briefly give the bulb direct power with a power probe it stays on and functions as it normally would.... as soon as i turn off the ignition and turn it back on i have the same problem (the light wont come on until i give it a jolt of power) any ideas???.... i am very frustrated and at my wits end .... thanks

[wiredgeorge]

My first suggestion is to list your bike's year and model. On newer bikes, there is a relay that allows the headlight to stay off for a bit when the key is turned on and it only comes on when the bike either starts or is turning over fast enough. If you have a newer bike, I think that might be the source of your problems or a connection to this relay. Without knowing what kind of bike, it isn't possible to give more specific advice. Older bikes (76 and earlier) had switches and were wired hot into the switched voltage... in other words, the light was on (if the switch was on) when the key was turned on and this produces a drain on the battery as voltage is especially low at that point.