tail light question

Michael xs650

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Whats up guys,
I have a tail light problem. When I turn the ignition key my tail light brightens up all the way as if the brake it consistently being pressed. Here is a diagram of how I have it wired. Bike is from 1975. Thanks.
 

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I can't tell much from your diagram but if I take it literally you have both filaments connected together, so if either gets power both will...
 
Do you have the tail light grounded? Where is says pressure switch that connector. Are all 4 of those wires connected together? They shouldn't be. The switch needs to have one end connected to power and the other end connected to the "brake" light for it to go off when the switch is "pressed". like this pic below

EDIT: I forgot to illustrate that the tail light has to be grounded. A pic of your tail light will help also.
 

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So, you need a common earth from the bulb holder to the frame( assuming its a -ve frame) then, depending on the bulb type, you will need one wire back to a switched +ve from the headlight switch, plus a wire back to the pressure brake switch from a +ve feed.
Effectively, it's one bulb with two circuits, with two switches through a common earth. When either switch is activated, you get the correct filament illuminating. It's always worth checking on the bench with a test battery to establish which connection is associated with each filament.
Hope this helps
 
Do you have the tail light grounded? Where is says pressure switch that connector. Are all 4 of those wires connected together? They shouldn't be. The switch needs to have one end connected to power and the other end connected to the "brake" light for it to go off when the switch is "pressed". like this pic below

EDIT: I forgot to illustrate that the tail light has to be grounded. A pic of your tail light will help also.

The diagram in this post would work.
 
It doesn't matter which + or - wire is connected a switch needs to interrupt a circuit. Some tail light will have 3 wires one being a ground and others will use the bulb housing connected to the frame assuming its grounded(should be) but you have to make sure any paint or rubber washers or anything isn't keeping you from grounding. So here we have 2 wires one is running and one is brake. You need to see which is brighter(stop) and connect that to the switch. Using a battery as XJ said is an easy way to do this.
 
Ok so I followed the diagram from above (thank you detale) and was able to get the switch to work properly. But... like always something goes wrong. My fuse kept burning out... I was able to ride a few blocks at first before the first fuse blew, I replaced it and was only able to go a very short while before the second one went. I had to call my sister to bring me some tools to re-wire it the original way and off I went back home. I can't figure out way this would happen if I didn't add any new lines but just wired it slightly different ( just like above diagram). Any ideas ? Maybe a ground issue ?

Here is my wiring set up :
 

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^If it doesn't blow in your first diagram and then blows with Detale's change it makes me think that what you've wired isn't Detale's change exactly. One thing it could be is that when you think you have Detale's change wired in in fact one side of the switch goes straight to ground so that when you hit the switch it takes 12v to ground and blows a fuse.
 
I can't see why it would blow a fuse.

What I do recommend to everyone is if you have a blade type fuse get a blade type circuit breaker that auto resets. It WILL save you time and money when trying to figure out wiring problems. Also if you blow all you have to do is shut off the ignition then it resets itself. Much better than having to change the damn fuse/run out of fuses and need to run to pep boys...

At the tail light what are you grounding to exactly? Do you have pictures of what you did, that might help. Is the switch in the ground or the power wire? How many amps on the fuse youre running?
 
Here are some pictures of my tail light and switch (don't know if it will help much) I am using 20 amp fuses and they are the blade type.
As far as a ground on the tail light I'm not sure.... There are only two wires feeding out of it and one is connected to headlight and ignition, the other is connected to pressure switch.
 

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Hmmm, odd. How are you joining your connections? Tape, spade connectors? Is it possible you pulled on a wire trying to make it reach? There's a short obviously. You could try and cap off both power to the light and take it for a spin to see if it blows then. At least you would know if it was th light. Also open up the tail light and check for loose connections there.
 
Found the problem. Two exposed wires coming from the pressure switch. Slapped some heat shrink on them and off I went. Thanks for all the replies, you guys are the best !
 
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