Electrical system on my '04 Dyna FXDP with carbed TC88A has failed totally twice in the past week. Hoping someone can suggest a fix.

When it fails, everything goes out; lights, gauges, ignition, total electrical failure. Happened at work last week when I went to start it cold to go home; nothing, no response to ign switch at all. Left it & caught a ride home and the next day, it came alive just like normal. Rode it home & dismantled/cleaned/greased the OEM ign switch thinking that was likely it. Ran fine for three days, then yesterday I was riding down the road at 65 perfectly normally and suddenly everything died, including the ignition! After I drifted to the side of the road, I did some troubleshooting (unsuccessfully) with my VOM and here's what I found:

40a Maxifuse was good/new; 12.88v found at battery/starter side of Maxifuse connector (battery is new, connections tight); only 5.6v (& unsteady) found at ign end of hot lead from Maxifuse to ign switch; zero ohms resistance in wire from Maxifuse to ign;

Here's the wierd thing: with ign switch in "Off" position, the speedo needle jumps very slightly & makes that slight spinning noise it normally does with first turned on. It does that for maybe 10 sec, then stops. I have to pull the Maxifuse to keep it from doing that.

It came back alive later today (inexplicably & for no apparent reason) and like last week, worked just fine! After it came back to life, the voltage at the power lead to the ign switch showed 12.75v. I pulled codes & a U1097 was set on the TSM Codes marker (S). I jiggled/checked all ground wires & connections - all appeared good.

Why on earth would there be full battery voltage into the Maxifuse, but only 5.6v at the ign switch when it is in limbo? Could there be a problem with regulator or alternator killing power from battery? Based on wiring diagrams, that's the only connection tapping into the power lead from the Maxifuse to the ign switch.

This intermittent failure is really shaking my confidence in (a) me & (b) the bike.

Any thoughts?

 

The other circuit tapping into that wire is the 15amp battery fuse that runs direct to the ignition module, it becomes a brown/grey wire after the battery fuse and only runs to the ignition module.

Cant help much but disconnecting the regulator is easy and bypassing the ignition switch is easy as well and since you are not blowing fuses it has to be something in that circuit.

Also check the crimps on the connectors for any loose ones as that can cause issues as well.

 

Scotty, thanks for input.

I actually made a ign switch bypass hot wire after the 1st failure & had it with me when it failed the 2nd time on the road. Using it to bypass the ign made no difference.

However, I didn't think to disconnect the reg/alternator connector to cut it out of the circuit. Might try that. If it works, there just might be enough juice in the batter to at least get me home. Good suggestion, I'll try it. Wish I had a headlight cutout switch.

 

Pull the ights fuse to save the battery and you can actually go a fair way with the regulator disconnected.