I have a 2009 Nightster that's been experiencing an overnight battery drain.

One day, the bike would stay on even with the key out of the ignition and the run switch set to off.

I brought it in to the dealership and they cleaned the fuse box, put in some dielectric grease, hosed down the bike and its been working ok but I still get the overnight battery drain.

Some days, its not so bad (slow cranking but still starts) but on others, it is enough so that the bike would not start.

I now keep it on the tender all the time to avoid the problem but when on a trip, that's not always easy to do.

The bike is charging fine and the battery is new. The bike's battery is always at full charge after a ride (coming home from work) so I know that the charging system is ok.

I called the dealer again and they say that it might be the ignition switch. Does that make sense to you guys? My appointment with them is in 2 weeks. in the meantime, the bike goes on the charger when its home.

 

Check your relays. you may need to replace them all together. I had that issue when i first got my bike. Replaced the relays and problem was gone. The 09 has a terrible fuse box design which does not protect the relays or fuses from water very well. You should probably get a few extra relays while you are at it for future issues. Oh and dont go to the dealer they charge too much for those damn relays

 

had that happen to my nightster it was the voltage reg

 

+1 - I would replace the relays first, they're common automotive relays that are inexpensive and available at most auto parts stores.

Part Numbers:
OEM is an Omron 2165A21A
NAPA is AR614
ABC Auto parts is STD RY302.

 

have the battery load tested..it may be going bad....

 

An ammeter should be able to quickly isolate what is drawing power. What was your last mod?

 

Good point. I could put the ammeter in series with the battery and remove one relay/fuse at a time.

The bike has no electrical mods.

the dealer sells the relays at about 10.00 each. Its cheap enough to try but I'll measure the current draw first.

 

With a meter like this, you can simply position it over the wire and read amps, directly. (the ad says GearWrench but it is K-D Tools) For less than $20 it can be useful for isolating faults. And it is only about as big as a saltine cracker, so fits easily in your troubleshooting kit.

 

This gauge probably won't be much help if you're looking for a slow (overnight or longer) discharge. In these cases, the battery draw is usually less that 1 amp which is going to be hard to see on a 75 amp scale.

Most digital multimeters can measure current up to a max of 2 amps.

 

With the key @ the off position, the current draw is 110ma. In the accessory position, the draw is approx 130ma.

I removed the relays with the key in the off position but the current draw stayed at 110ma so the relays look like they're ok.

However, when I removed and re-inserted the acc. fuse, the current draw would sometimes drop to 67ma. Also, when I wiggled the key in the off position, the current draw would sometimes drop to 67ma as well.
Then, I removed all relays and fuses from the fuse box except the 15a battery fuse and still had between 67ma and 100ma draw ???

Looks like the ignition switch might be the problem after all, but I wonder... what is the normal current draw on these bikes when the key is in the Off position?

I'd like to check the current draw with the tssm unplugged as well. Where is it located?