I have a 2000 Softail standard. My bike blew a fuse for spedo and brake light. Then it blew head light and tail light fuse when I stuck new one in the speedo/brake slot. Can't have both fuses in. Also I noticed when I have key turned to accessories and squeeze the brake lever my headlights and brake lights come on, but when key is on the tail light come on but brake light will not light up. I hope all that makes sense. Just looking for suggestions. Thanks

 

I always start with battery cables, specifically grounds, on any electrical problem. However with blowing fuses, that will probably not be the source of your issue.

Do you have any mods to your lighting system(s).....?? Any add-on modules for any lighting options? They can go bad, and when they do, weird things just start happening..

For example: I had a run/turn/brake module on my 2003 bike for the rear turn signals. It ran great for 15 years. Then all of a sudden, my turn signals started to activate opposite from the turn signal button I pushed...?? I removed the old module, all went back to normal OEM operation. I bought and installed a new R/T/B module and now all is well again..

If no add-on modules, it would appear you have a short somewhere you need to trace down. Off the top of my head, I can't think of a connection between the headlight/stoplight circuit and your speedo/brake light circuit, other than the actual tail light fixture... Since you say you can't have both fuses in at the same time, I would start at the tail light fixture, looking for anything that can "bridge" those two circuits to cause a short between them... like excessive moisture, broken wires, bad bulb base, etc..

Expand your search from there, looking for bad wires/switches...

Eventually you will need to check all fuses and bulbs, as some may be collateral damage from the initial problem.

A good "while-you-are-at-it" would be a thorough inspection of your Ignition switch. Be sure to check connections and contacts internal to the switch. There have been threads about the older Twin Cam ignition switches wearing out, and causing a host of issues.... Many of the problem ones needed to have a thorough cleaning and some needed replacement.

Electrical issues require patience and persistence to track down... good luck with your repair..

 

Sorry double post.

 

Fuel injected or carb (they have different wiring diagrams)?

Tell us the names of the fuses that are blowing.

I think hattitude is on the right track about wiring in the tail light area, check the wiring harness underneath the rear fender, they get damaged all the time.

An easy way to isolate the rear wiring harness would be to unplug the connector for the rear harness, then install new fuses and see if the problem persists.

 

One and done...