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1994 Ducati Super Sport 900 CR
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69 Posts
Discussion Starter #21
I said it earlier but I guess I should say it again: there are two wires that go to the tail light assembly. One wire is to the brighter brake light and one is to the dimmer tail light. If the tail light wire is directed to the brake light, the brake light will illuminate when the bike is turned on. When you apply the brake, the tail light bulb will illuminate but because it's dimmer than the brake light, it's hard to see.

I would investigate that first before doing anything else.
Yessir agreed that is the starting point 馃憣
 

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1994 Ducati Super Sport 900 CR
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69 Posts
Discussion Starter #22
Hi Everyone, I just picked up my first Ducati, its a 1994 Super Sport and i am STOKED! On the way home from the sellers my wife noticed i didn't have any lights on the rear tail light at all (no running lights, no brake lights). The first thing i thought of was the bulb was burned out....simple. No, not simple. I replaced the bulb with a 2 filament 1157 i bought new. Now, the brake lights on all the time (both filaments are lit). So i thought, hey, one of the micro switches for the front brake lever or the rear must be stuck in ON position. So, I started to disassemble the areas to gain access to the switches. I did so (after breaking a bolt off on the rear peg set :(!. Anyways, here's where it gets interesting. So with the rear switch in the OFF position (not braking) and the front switch in the OFF position (not braking) the tail light is still on...both elements. With the rear switch in the OFF position and the front in ON position (when you'd squeeze the lever to brake) one element will turn off on the tail light. I checked to ensure i'm inserting the bulb correctly. The rear switch will very faintly try to cut out the second element in the ON position but is really ineffective. Oddly, the receptacle for the rear bulb has 3 slots, the 1157 has 2 slots. Any help is appreciated as riding without brake lights isn't an option:) View attachment 988789
Update, just for fun i used a test light that has a voltage readout on it. With both brakes off both copper strips are hot with 9volts, And, with brakes on its the same the same. The socket tabs are really tarnished and you can manipulate the bulb in and out a bit. My other thread is about trying to remove a broken bolt on the right rear set...where the bike has a wire jumper from the front to back on that bolt. The guys were saying that if that ground is compromised it'd mess up the electrics on back of the bike. The adventure continues...the only saving grace is our DMV is so backed up in Colorado i can't get plates until the 31st of July so at least i have time right??
 

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My recollection, perhaps faulty, is that the brake switches act on the return leg to ground. If I'm correct, there will always be voltage at the lamps and switching the ground completes the circuit. I wouldn't expect the voltage to be 9V however. What is your battery voltage?
 

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1994 Ducati Super Sport 900 CR
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69 Posts
Discussion Starter #24
My battery volts is 12 last time I checked a few days ago. I'll recheck and see this evening
 

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2001 900SSie
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I looked at the wiring diagram.
One side of each brake switch goes to the fuse block, so is powered and each switch provides power to the bulb.
The cylindrical case of the bulb is grounded.
1 - agree with Spacey that 9V is strange. With the minuscule current drawn by the meter when reading voltage would not induce a voltage drop.
2 - maybe one or both of your brake switches is jammed closed. The tail light will always have voltage at key on.
Unplug one switch then the other to see if that is the case.
 
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1994 Ducati Super Sport 900 CR
Joined
69 Posts
Discussion Starter #26
I looked at the wiring diagram.
One side of each brake switch goes to the fuse block, so is powered and each switch provides power to the bulb.
The cylindrical case of the bulb is grounded.
1 - agree with Spacey that 9V is strange. With the minuscule current drawn by the meter when reading voltage would not induce a voltage drop.
2 - maybe one or both of your brake switches is jammed closed. The tail light will always have voltage at key on.
Unplug one switch then the other to see if that is the case.
Thank you Punch i will do some some troubleshooting this weekend including this suggestion!
 

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1994 Ducati Super Sport 900 CR
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69 Posts
Discussion Starter #27
My recollection, perhaps faulty, is that the brake switches act on the return leg to ground. If I'm correct, there will always be voltage at the lamps and switching the ground completes the circuit. I wouldn't expect the voltage to be 9V however. What is your battery voltage?
Just checked the voltage, its a hair over 12.5, so that's good! I am going to try advice offered by you guys this weekend. This forum is completely awesome! Thank you everyone :)
 

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1994 Ducati Super Sport 900 CR
Joined
69 Posts
Discussion Starter #28
Hi Everyone, I just picked up my first Ducati, its a 1994 Super Sport and i am STOKED! On the way home from the sellers my wife noticed i didn't have any lights on the rear tail light at all (no running lights, no brake lights). The first thing i thought of was the bulb was burned out....simple. No, not simple. I replaced the bulb with a 2 filament 1157 i bought new. Now, the brake lights on all the time (both filaments are lit). So i thought, hey, one of the micro switches for the front brake lever or the rear must be stuck in ON position. So, I started to disassemble the areas to gain access to the switches. I did so (after breaking a bolt off on the rear peg set :(!. Anyways, here's where it gets interesting. So with the rear switch in the OFF position (not braking) and the front switch in the OFF position (not braking) the tail light is still on...both elements. With the rear switch in the OFF position and the front in ON position (when you'd squeeze the lever to brake) one element will turn off on the tail light. I checked to ensure i'm inserting the bulb correctly. The rear switch will very faintly try to cut out the second element in the ON position but is really ineffective. Oddly, the receptacle for the rear bulb has 3 slots, the 1157 has 2 slots. Any help is appreciated as riding without brake lights isn't an option:) View attachment 988789
Everyone, the electrical gods willing with your help ill get this resolved this weekend, Ill most definitely let y'all know what it was when I solve it....with your help!
 

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1994 Ducati Super Sport 900 CR
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69 Posts
Discussion Starter #29
Just throwing this out, but would it be possible to add a small drop of solder to the bulb in the location where it is not properly contacting to increase its size?
Ya, maybe, to decrease the diameter of the socket?
 

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1994 Ducati Super Sport 900 CR
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69 Posts
Discussion Starter #30
Hi Everyone, I just picked up my first Ducati, its a 1994 Super Sport and i am STOKED! On the way home from the sellers my wife noticed i didn't have any lights on the rear tail light at all (no running lights, no brake lights). The first thing i thought of was the bulb was burned out....simple. No, not simple. I replaced the bulb with a 2 filament 1157 i bought new. Now, the brake lights on all the time (both filaments are lit). So i thought, hey, one of the micro switches for the front brake lever or the rear must be stuck in ON position. So, I started to disassemble the areas to gain access to the switches. I did so (after breaking a bolt off on the rear peg set :(!. Anyways, here's where it gets interesting. So with the rear switch in the OFF position (not braking) and the front switch in the OFF position (not braking) the tail light is still on...both elements. With the rear switch in the OFF position and the front in ON position (when you'd squeeze the lever to brake) one element will turn off on the tail light. I checked to ensure i'm inserting the bulb correctly. The rear switch will very faintly try to cut out the second element in the ON position but is really ineffective. Oddly, the receptacle for the rear bulb has 3 slots, the 1157 has 2 slots. Any help is appreciated as riding without brake lights isn't an option:) View attachment 988789
Final update! The problem was fixed. It turned out to be a stuck rear brake sensor, but let me tell me how i got there. First off it was with every ones help here and a big THANK YOU is well deserved.

So I unhooked both brake switches and actuated each one with the other in neutral, sounds simple right? I made a large error though! I assumed that the front brake micro switch was ON with the plunger in, it was not. This one error made troubleshooting like chasing your tail. I learned to be more detail oriented next time and don't assume anything. Some other things I did for troubleshooting was right off the bat, make sure the power wires weren't reversed, next I purchased a new 1157 bulb socket and temporarily wired into the harness, it worked. I bench tested the original socket with a power supply, it worked too, so the socket wasn't an issue. I removed the little jumper harness off the rear brake switch and checked it for continuity, it was good. The best thing i did was de-solder the wires of the rear brake switch which enabled me to manually complete the circuit by hand (just touch the two wires together). When I did this the brake light came on every time (with the front off), and just for fun I re-soldered it tonight and reinstalled the switch and duplicated the brake light always on condition, i even got it to flash a few times with manual manipulation. So there you have it. New brake switch is ordered and on the way!
 

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Glad you got the brake switch figured out.

Look carefully at the existing bulb socket and compare it to the good new one you bought. See which one holds the bulb securely. If they both have any play side to side, then know that there are better ones available.
 

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1994 Ducati Super Sport 900 CR
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69 Posts
Discussion Starter #32
Glad you got the brake switch figured out.

Look carefully at the existing bulb socket and compare it to the good new one you bought. See which one holds the bulb securely. If they both have any play side to side, then know that there are better ones available.
Yes, I'm going to swap the stock one, way too much play! Note, be careful of socket depth if you do this. The one I had was too long, ordered shorter one from AMZ.
 

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1994 Ducati Super Sport 900 CR
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69 Posts
Discussion Starter #33
Yes, I'm going to swap the stock one, way too much play! Note, be careful of socket depth if you do this. The one I had was too long, ordered shorter one from AMZ.
I figured I would show the pics from the socket swap. I removed the old socket holder from the tail light plastic (via Dremel) and mounted a new 1157 unit which will accept the more modern / smaller diameter bulbs. The plastic adapters are made form PLA plastic that i made on my 3d printer, then I used a heat gun to form them to the curve. They're glued on and the sockets glued on to them. If anyone wants these plates just let me know and i'll send them to ya.
990615
20200720_181320.jpg 20200719_161555.jpg 20200720_181331.jpg
 

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With an 1157 LED bulb it should be bright enough, but painting it chrome wouldn't hurt. Looks like a good job, well done.
 
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