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My 2003 Deuce has been sitting in the garage as it normally does over the "winter" in east TN and I discovered that the brake light it staying on all the time. Here is what I have tested:
The front switch is working as it should - I stuck a needle probe into both wires coming off the switch and can make the voltage go from zero to 14 by pulling the lever. The rear light itself is aftermarket LED but still has independent running and brake light circuits working - I tested them off the battery. The rear brake switch seems to be stuck on because it has 14 volts going in and coming out - but if I unplug one of the wires the brake light stays on.
The tail light and brake light circuits coming from the front harness (from under the tank) and connecting to the rear harness under the seat are on with 14 volts constantly.
Funny fact... in the ACC position neither the tail light or the brake light comes on as they should... I'm having a bit of trouble figuring out what else is between the harness connection under the seat and the individual front/rear switches.
Looking for a wiring diagram for this bike is like a maze of internet search "bait & switch" bullshit - but maybe I'm just too cheap to by the manual. I like to beat "the man".
Any suggestions on what is causing this or should I just man up and buy the &@##$!! manual? Tim B.
Maybe I misread, but it sounds like the rear switch. If voltage is passing through even when the switch isn't activated, it sounds like that is the problem. Maybe I misread? If the wiring is completely removed from the rear switch does the light go out? Sorry, the electrical side isn't my thing.
Thanks for the suggestions etc. guys... here is my latest.
I split the clamshell on the right handlebar and put a needle probe thru the insulation on the front brake light switch.
As you can see from the multimeter I was able to open and close the circuit by pushing the switch button with my finger.
I put the multimeter on the rear switch - both wires - and got 15+ volts off each wire without the rear brake pedal engaged.
This would suggest that the rear brake switch is bad or there is pressure closing the circuit.. BUT
Now for the kicker... wait for it... I unplugged both rear brake switch wires and the #$%@! rear brake light still stays on with the front handle not pulled!
WTF?
Front Brake switch circuit open - button in
Front Brake switch circuit closed - button out
Rear Brake switch top wire - power there - no pedal pressure
Rear Brake switch bottom wire - power there too with no pedal pressure!
Once again....If the Red/Yellow wire is removed from the rear switch, that switch is removed from the circuit, it cannot possibly be sending power to the brake light.
The problem is not the rear brake light switch.
The only other source of voltage to the brake light is from the front switch, and that is where your problem is.
When the brake lever is released, the plunger in the switch is not being pushed in far enough to open the electrical contacts.
Stop poking holes in the insulation on the wiring...
In the illustration below I highlighted in red the wire that runs from the front switch to the brake light (the actual color of the wire is Red/Yellow).
Last edited by Dan89FLSTC; Mar 24, 2022 at 10:12 PM.
Thanks for your comments and the wiring diagram Dan, I agree that if the rear switch is unplugged it cannot be the problem.
I bought the Haynes manual and looked at the wiring diagram too and I agree with you that the front switch is the only other plausible source of power to the brake light.
However, I can't square that with the fact that that switch appears to be working as tested with my multimeter.
I don't relish the thought of soldering in a new switch but that is what I may have to do if I can't find any other explanation.
Any thoughts on why the running light doesn't come on when the switch is in the ACC position? Could it be related?
Electrical problems have always been some of the most challenging for me.
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Brake Light on all the time!
