Amperage Draw of Fuel Injected Harley’s

Here are some “average” amp draw amounts for the different circuits on a fuel injected Harley-Davidson. These were taken off of a 2009 Softail Heritage. I took them at the fuse (relay) box looking for a bad component that was drawing a lot of power. In this case it ended up being a bad tail light flasher thing made by BikeTronics. While these figures are for the Softail, these figures will be about the same for almost all bikes. Example a headlight circuit will pretty much draw the same power. Same thing with the ECM’s.

  • Tail Light 1.5 amps
  • Head Light 4.4 amps
  • Head Light + spot lamps 7.8 amps
  • ECM 5.2-5.5 amps (varies due to injector driver circuit)
  • Ignition .2 amps
  • Speedometer .2 amps
  • Key Off, battery draw .2 amps

In my case, the tail light circuit was drawing 4 to 5 amps and this seemed weird because I knew from testing things all the time, that 1157 tail light bulbs generally draw 2 amps. By luck since this thing just plugged in, I took it out of circuit and the tail light then drew the 1.5 amps. The part was not burnt or looked damaged in any way. I believe it also did something with the blinkers, running lights maybe? Don’t remember, honestly.

The original problem the bike came in for was bad charging system, not charging. The stator wasn’t putting out and you could see it got hot. I replaced everything with new, good parts, (regulator and stator, and it had a brand new battery) and it charged, but it was charging low. It was just barely charging at 13.5 volts @ over 2500 rpm. Most modern Harley’s charge @ 14.2 volts at idle or just off idle.

I mention this because you should always investigate something if you think it isn’t quite right. I could have technically sent it out the door, charging and fixed, but it would have eventually been back with the same problem.

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