Brake switch/battery question
Seasoned HDF Member
Joined: Aug 2006
Posts: 24,528
Likes: 30,847
From: Pennsylvania
Disconnect your voltage regulator and perform the parasitic test again and let us know if the reading changes. You should just be able to unplug it for the test.
Stellar HDF Member
Joined: Aug 2011
Posts: 2,767
Likes: 1,802
From: Newnan, GA
Situation: front brake switch bad - wont activate stoplight. Tried electronic cleaner. Rear switch does produce stoplight.
question: can bad brake switch possibly cause drain on battery? I can live without hand activating stoplight, just remember it requires foot activating stoplight. Trying to avoid the tight fitting soldering etc. but will do if thats causing the battery drain every few days. H-D Battery is two and half yrs old.
tia
question: can bad brake switch possibly cause drain on battery? I can live without hand activating stoplight, just remember it requires foot activating stoplight. Trying to avoid the tight fitting soldering etc. but will do if thats causing the battery drain every few days. H-D Battery is two and half yrs old.
tia
You may have a parasitic draw from somewhere else on what ever bike that you have.
Thread Starter
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Cruiser
Joined: Sep 2006
Posts: 212
Likes: 31
did as you suggested and reading is same.
Seasoned HDF Member
Joined: Aug 2006
Posts: 24,528
Likes: 30,847
From: Pennsylvania
Okay, sometimes depending on how the voltage regulator is configured, one of the diodes could be shorted and bleed off voltage when shut off.
I had an issue with one of my Honda's and it confounded me for a long time, would show charging as it had 3 diodes and one was shorted. Finely tested the regulator and it showed one diode bad.
Did not know if yours was the same but if the reading did not change, your regulator is probably good..
I had an issue with one of my Honda's and it confounded me for a long time, would show charging as it had 3 diodes and one was shorted. Finely tested the regulator and it showed one diode bad.
Did not know if yours was the same but if the reading did not change, your regulator is probably good..
Seasoned HDF Member
Joined: Apr 2018
Posts: 5,947
Likes: 5,147
From: Louisiana
All Harley’s are not the same. A parasitic drain can be different for different Harleys. The normal parasitic drain on a Harley Softail battery should ideally be around 20 to 50 milliamps, and some say 50-85ma if you have the smart security system.. I’ve heard some say 6ma is max without security. So, I’m a bit over my head here.
Do you have a smart security system?
I would also suggest using a battery tender. I keep one plugged up to both my bikes plus tractor, boat, lawnmower and sometimes my Jeep if it’s not driven much.
Do you have a smart security system?
Battery drainage on modern Harleys is often caused by the smart security system that continuously monitors the bike even when parked.
Harley-Davidson Technical Service Bulletin 2024-ELEC-03
Harley-Davidson Technical Service Bulletin 2024-ELEC-03
I would also suggest using a battery tender. I keep one plugged up to both my bikes plus tractor, boat, lawnmower and sometimes my Jeep if it’s not driven much.
Last edited by Down South; Oct 5, 2025 at 07:55 PM.
Seasoned HDF Member
Joined: Apr 2018
Posts: 5,947
Likes: 5,147
From: Louisiana
One other question, if you have a smart security system Proximity fob, do you store the fob close to the bike? If so, that prevents the security system from going into sleep mode and creates much more draw on the battery.
Also, again if you have a smart security system, do your ma draw test with the fob out of range of the bike.
Also, again if you have a smart security system, do your ma draw test with the fob out of range of the bike.
Last edited by Down South; Oct 6, 2025 at 02:28 PM.
Thread Starter
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Cruiser
Joined: Sep 2006
Posts: 212
Likes: 31
One other question, if you have a smart security system Proximity fob, do you store the fob close to the bike? If so, that prevents the security system from going into sleep mode and creates much more draw on the battery.
Also, again if you have a smart security system, do your ma draw test with the fob out of range of the bike.
Also, again if you have a smart security system, do your ma draw test with the fob out of range of the bike.
Seasoned HDF Member
Joined: Apr 2018
Posts: 5,947
Likes: 5,147
From: Louisiana
Just suggestions, A security system can pull a battery down within a week or so by itself. I had to go back through the whole thread to come up with something. If you pulled all of the fuses and the only one that made a difference was the battery fuse,
Unplug the main fuse and do an amp draw from the fuse holder. That will kill power to the EMC. That will kill power to everything.
If you have a good reading from the main fuse holder, reinstall the main fuse and disconnect the ECM and see what the reading is. Although the EMC should be powered from one of the fuses under the seat.
Leave the key fob out of range of the bike.
So, after neg cable off overnight I did a voltage test and got 12.48v (little low?).
performed drain test and got .1 on 10A setting and 109 on 200mA setting. My understanding is it should be under 50mA.
I pull one fuse at a time and the only one that made reading go to 0 was the one marked “battery “. With all the others reading stayed the same.
I’m not sure of next move except to monitor voltage periodically as battery sits disconnected.
any information or suggestions appreciated.
tia
performed drain test and got .1 on 10A setting and 109 on 200mA setting. My understanding is it should be under 50mA.
I pull one fuse at a time and the only one that made reading go to 0 was the one marked “battery “. With all the others reading stayed the same.
I’m not sure of next move except to monitor voltage periodically as battery sits disconnected.
any information or suggestions appreciated.
tia
If you have a good reading from the main fuse holder, reinstall the main fuse and disconnect the ECM and see what the reading is. Although the EMC should be powered from one of the fuses under the seat.
Leave the key fob out of range of the bike.
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Road Warrior
Joined: May 2025
Posts: 1,284
Likes: 658
From: Eastpointe, MI
Is this the norm?
There is nothing in Michigan, never has been.
They tried it with automobiles 30 or 40 years ago and it was a disaster they stopped it.
(But yeah I wouldn't ride without both my brakes activating the stoplight, just like wearing a helmet or pants - I don't need the government to tell me that).
Googled it - 15 states don't, 35 do.
Last edited by Robertbc3141; Oct 8, 2025 at 06:20 AM.