Found several useful posts on similar scenarios but nothing that quite addressed my issue so I thought I'd share what I went through in the hopes it helps somebody else down the road.

Bought a 2007 Fatboy 3 weeks ago. Bike has had some minor electrical mods; connector for trickle charger & red rear turn signal/triple brake light set-up in place of the standard single brake light/amber signals. Last week the turn signals stopped working & discovered the brake light wasn't working either. A little online research quickly showed I had blown the Accessory fuse. So, I replaced it & it was blown again in less than a mile.

Experimentation & a few more blown fuses showed this was specific to the right turn signal. Left signal was fine. Applying front or rear brake was fine. The right turn signal button may as well have said "press here to blow Accessory fuse". Sounds like a short. Yup, I thought so too. But, the $64,000 question is of course - where?

I checked/swapped bulbs front & rear, eyeballed wires in the rear fender, checked for trouble codes (none), disassembled the right turn signal switch housing to check for pinched wires & even pulled the TSM hoping to interrupt the short (I don't think I did this right though, as my Ohm-meter still showed a short on the wire I was connected to after I found the issue). Nothing.

Finally, as I was futzing around the battery compartment area I noticed a black mark on a white wire that was going right by the negative battery post. Dunno if the battery in there is "taller" than the original or what but thank goodness the wire wasn't purple or brown or something & I could see that mark easily. I pulled it away from the battery terminal & wah-lah! Good turn signal. I wrapped the "wound" in electrical tape & jammed a plastic Romex staple "bridge" in there (sans nails of course) & the fix is in; albeit a little cheesy.

 

That wire should be white with a brown stripe to do what you are saying.

 

Correct-a-mundo! Was just happy I could see the other brown stripe.

 

All was well for a few weeks. I honestly don't remember how many times (more than a couple; probably less than 20) before I had more issues but an early October ride to work ended with a ride home on a flatbed tow truck. The bike would not crank & the "key" light was on. There's not a whole lot of riding here in Colorado once October hits, at least for warm-weather guys like me (Yes, my brother tells me there's another word for that.) so, I left it until spring.

I pulled codes sometime this winter & I had: P - U1064 (loss of TSM serial data), S - B1141 (TSM – Ignition SW low/open), SP - U1064 & U1255 (Serial data Error/Missing message). Research made it sound like the TSM wasn’t getting proper feedback…?

I did remove the TSM when I was trying to diag the original issue. But, disconnecting/reconnecting that thing seemed pretty straightforward. So, I figured the afflicted turn signal wire had been burned a little too much & cut it at the burn/break reconnecting it with a heat shrink butt-connector, & cleared the codes. It started right up & I took it for a run one mile up the road to my brother’s place. It would not start after shutting it down but he’s all uphill from me so I started it by popping the clutch while rolling back down the hill. When I pulled the codes again they were identical to the first set. I pulled the seat off & my cheesy nylon “U” bridge had fallen out. I also noticed the LF turn signal bulb was blown. I replaced the bulb & tried to cause any short by jiggling wires under the seat with the right turn signal flashing while it was sitting – not running - in the garage. No problems. So, I re-crimped the connector, replaced the nylon “U” & cleared the codes again.

I took it for a ride & everything was fine – for about 10 minutes. Then, I got the “key” indicator light again & the right turn signal stopped working. The left turn signal was okay. I brought it right home & pulled codes again. This time: P – none, S – B1122, B1141, SP – none. The B1122 was new & indicated an open on the right signal so I figured the connector I’d installed wasn’t doing the job all the time. I cut out the connector I was using as well as part of the wire that was pulled into a right angle because of all this (in case I’d broken enough strands to cause a problem) & added a length of new wire with 2 new connections. I twisted both connections together each with a good half inch plus of wire to make sure there was plenty of contact adding heat shrink over the new connections for insulation.

This test drive was very similar to the last. It was fine for several minutes. I even turned on the right turn signal several times when it was not needed as I was driving down the road. Everything was good; no “key” indicator, turn signals worked fine – until somewhere around 10 minutes into the ride. Then the “key” light came on & the right turn signal stopped working. The left turn signal continued to work for a short while. Then, it too went out & I had no turn signals. Again, the bike never sputtered; it runs like a top. But, the turn signals were both gone. Besides the “key” light, I also got the CEL too. When I got home, I pulled codes again & I have: P – U1064, S – no rsp, SP- U1064, U1255.

Some of the stuff I have run across has referred to “remarrying” the TSM & ECM but the bike – when it has started – runs flawlessly & it has never thrown a P1009 code which it seems like it would if the TSM were not properly connected. Could I have fried that thing – at least partially – with the initial short even though it was popping fuses? Or, am I chasing the wrong thing completely & I should be looking elsewhere?

 

For the benefit of anyone looking at this (I hate threads that leave you hanging.) the TSM was indeed bad. The Electronics Diag Manual said (for one of those DTCs; I forget which.) to pull the TSM & check the connector block for current on the turn signal circuit with the ignition on. If it has current you still need to find a short. If not the TSM is bad. It checked out good (i.e. no shorts) so I replaced the TSM & it's been fine for a month.