I'm hoping someone might be able to let me know if I'm on the right track.

When my 03 Ultra gets hot the 50 amp circuit breaker under the seat trips and all DC power is cut. I think the voltage regulator may be grounding when hot or the circuit breaker itself may be faulting out. The first few times it happened it was just momentary and power came back and the bike started back up since I was moving. I didn't even fully realize what was happenig it happened so fast. Then it got worse and the breaker would stay open longer, upto a couple of minutes before I could restart the bike. Luckily this has only happened at low speed or when stopped and I have been able to safely get out of the way of traffic.

So far during my troubleshooting I found a loose nut on the right side ground at the frame under the seat. It wasn't even finger tight. I tightened it and the the breaker still tripped after idleing for 5 min.

I am considering disconnecting the voltage regulator and running off the battery to determine if the VR or Stator may be shorting when hot and causing the breaker to trip. If this is the problem then it shouldn't die as long as my battery charge holds.

I will also replace the circuit breaker before I'm done since it is probly getting weak from tripping so many times.

By the way I've looked for shorted wires and bad connections and will continue to do so as I troubleshoot.

this only happens when the bike is hot (stuck in traffic or at a long light when the air temp outside is up in the high 80s or above). It's never happened when air flow has been good, even during city riding.

If anyone has an idea of something that may cause this to happen please let me know. Any good advice on troubleshooting this issue would be appreciated also.

 

I have a friend that rides and 03 Ultra that is having exactly the same problem. He losses all electrical power but after a couple of minutes, it starts just fine.

He has noticed that his voltage guage shows only 14 volts when riding which is low compared to mine and a couple of other bikes which are around 15 or so.

Just wanted to let you know your not the only one. Might be a common problem with Harleys in general or maybe just the 03.

I love riding Harley's but there seems to always be something to fix.

 

The breaker trips due to excessive current. If it trips while stopped it looks like a heat issue. Do you have alot of lights or anything else that would generate heat? Try to recreate the condition in your garage/driveway and then touch the regulator to see if it's hot...A short will cause the regulator to get hot...

I've also seen neutral switches short to ground and load the charging system down....I'm only throwing out basic stuff here. Electrical issues can be a real pain in the *** to isolate especially the type you have which is intermittent...The hardest part is to recreate the condition and find the problem before it goes away! I feel your pain! Been there too many times!

 

Does anyone have the wiring scehatics for an 03 ultra. I have them for an 04 but I know there are some differences. For example the 04 has a maxi fuse instead of a circuit breaker.

 

Does anyone know for sure what voltage the regulator should be putting out when it's under full load?

 

Heat is how these things trip and break contact. If it's picking up a lot of extra heat not related to actual current draw it will trip sooner than it's rated for. It also could be crap and tripping before its rated amperage.
The bikes systems could be completely ok in these cases.
Ron

 

Check the connections at the circuit breaker for corrosion or loose connection. Be sure the batter cables are tight.

 

There was a problem with the circuit breakers themselves from 2001-2003
here is the tsb

http://www.pvc.maricopa.edu/~preston/M1151.pdf

 

Did you pick up on the fact that the 40s were tripping and they stuck in a 50 for the fix. Sounds more like a design miscalculation.
Ron

 

Good news!!!!! I finally fixed the problem on my bike. Took about 15 minutes and a 10 cent part to do the job. AS it turns out, the breaker wasn’t tripping due to excess current flow caused by a intermittent short as I first suspected. My amp clamp proved that the breaker would trip even though the bike was pulling less than 30 amps with everything on including break light and 4way flashers. While prodding around the breaker with everything on, I found that the main power wire that leads from the silver post on the breaker to the ignition switch was hot to the touch near the breaker. This heat was being transferred through the post into the breaker causing the breaker to trip due to the external heat source, not heat caused by excess current as the breaker was designed. I hadn’t found this before because I hadn’t had my hand in there with everything on. Being an electronics tech by trade, I’ve learned to keep my hands away from energized equipment when possible (let me just say I learned that the hard way). I had previously used an ohm meter to check all the connections at the breaker and battery for any resistance and all were good. AS it turns out the heat was being caused by corrosion inside the terminal lug. But there wasn’t any visible evidence of corrosion or excess heat to be seen. I used a needle probe on my meter to penetrate the insulation on the wire and determined there was resistance at the crimp on the lug. When I pulled on the wire a little the resistance dropped to almost zero. All of this explains why the problem was so intermittent and more prevalent on hot days. Anyway, to make a long story a short, I replaced the lug and with the breaker I had already replaced, my total cost was just over $7 and a little time. A lot better than taking it to a shop. Score 1 for a DIYer
By the way, I also recommend using an oxide inhibiting compound on these types of connections. You can get it at any electrical supply store.
I’m sorry about the long post but maybe it will help someone else find a similar problem.

Ride Safe and thanks for the help