Only rear running light or license plate light works on SM

Likes
0
Location
Maryland
#1
Hello all, I'm a bit new here but I've had my SM since may of 2018 with no real issues of any sort until lately.

I noticed one night that my rear brake light running light wasn't on, yet the license plate was good and so was the brake when applied from either or both levers. I tried to first turn the bike off and on, which makes it flicker for a moment but will still shut off. The bulb looked good and I replaced it anyway just to test. Same issue. So I dug under the rear fender to check connections, all good again and even tried unplugging and replugging, same issue.

The only way I could get the brake running light to work was to disconnect the license plate light. I'm realitively okay with this since I don't ride too often at night and haven't had any issues with cops since it first started but I was hoping to get some ideas or input from the experts.

Huuuuge thank you all in advance!
 

Rashid510

Well-known member
Forum's Sponsor
Likes
508
Location
South San Francisco, CA
#2
Easiest way to check for shorts or faults is using Multitool, which is the diagnostic system Alta created. There could be some dirt/debris in the rear harness. Or the harnessing to the lightbulb may have gotten loose.
 
Likes
0
Location
Maryland
#3
Thank you Rashid I will try to clean and check for debris weekend. I was planning on wrapping the plastics again so I'll have everything off the bike and can clean it all. I still need to make a multitool but it's on my list.

Just a curiosity question but if there was a short of some sort of short wouldn't that be more permanent to one thing? Like the brake light would never work even if I didn't unplug the license plate light? Or does Alta just use like two fuses for the rear and since there's a short somewhere it's tripping out of of them which has since gone bad and that's why it won't allow everything in the rear to work?

Like I said I don't know much about electronics, but I personally find it weird how if I just plugged the license plate back in it'll work fine but the running light will go back out and vice versa.
 

Rashid510

Well-known member
Forum's Sponsor
Likes
508
Location
South San Francisco, CA
#4
There arent fuses on the bike (like a fuse block). Sounds like a loose connection. Were any of the spade terminals for the light plugged in loose or wrong connection? We had some issues like this back in production which was related more to the bulb/wiring.
 
Likes
0
Location
Maryland
#5
Good to know! And unless a gremlin came in and changed my wiring it should have been the same, although connections especially back there could probably come loose naturally. I'll have to do a deeper dive closer to the light when I pop it off this weekend.

This definitely gives me a place to start with and test with what I have.

Huge thanks for the fast replies too, and the willingness to help!!
 

snydes

Moderator
Staff member
Likes
1,916
Location
Pennsylvania
#6
Don't hold me to this, but I somewhat remember a member having a similar problem that was resolved by trying a different bulb. The bulb still worked if I recall correctly, just was making the bike do funny things.
 

Similar threads