79 sportster charging problem

Discussion in 'Electrical' started by Smrtazz, Apr 24, 2016.

  1. Smrt1 Mark

    Smrt1 Mark Member

    14
    3
    2
    Hey guys, the origional post got deleted. I checked fuses as someone had suggested. The only one that has constant power is the ignition relay, and I believe that one needs it. I was wondering if anyone knows the answer to this. Should I be able to get a reading from the generator at the armature? While the bike is throttled up of course.
     
  2. Jack Klarich

    Jack Klarich Expert Member

    18,544
    153
    399
    Voltage Test

    With the generator mounted on the motorcycle disconnect the wires from the “A” and “F”terminals. Connect the red lead from a voltage meter to the “A” terminal. Connect the black lead to a good clean ground. Set the meter for a 20-volt DC scale and accelerate the motor to about 2500 RPM. The voltage meter should read a positive 2-4 volts DC. If you get no voltage or a negative voltage, try polarizing the generator. (See polarizing section) Polarizing will cure reversed voltage. After obtain a reading of 2-4 volts positive on the meter; leave the meter hooked-up the same and change to a 50-volt DC scale. Use a jumper wire and connect the “F” terminal on the generator to ground just long enough to read the meter. It should read a positive 40-50 volts. This shows with an open field circuit you have low voltage. With a closed field the voltage is high. It is the regulators job to keep the voltage at the proper level. If you get no voltage or low voltage the generator has a problem.
     
  3. Smrt1 Mark

    Smrt1 Mark Member

    14
    3
    2
    Thanks man, I just did it. Low voltage, the generator is weak. But it looks like the origional, after 37 years, its done it's job well
     
  4. tourbox

    tourbox Senior Member

    1,311
    68
    54
    It is probably your brushes worn out. If you don't feel confident replacing them yourself then a good starter/generator automotive shop can handle it.
    tourbox
     
  5. Smrt1 Mark

    Smrt1 Mark Member

    14
    3
    2
    Yea, I tore it off today after work. Found a generator/alternator shop near my job that will inspect it for free. I don't have a ammeter.
     
  6. Smrt1 Mark

    Smrt1 Mark Member

    14
    3
    2
    It was the brushes, the wire was frayed and back feeding, replaced it, put it on in between rain storms today. Gave it some throttle hit 13.32 and rising under throttle. Nothing but good news.:)
     
    Jack Klarich likes this.
  7. Jeff Klarich

    Jeff Klarich Well-Known Member Contributor

    3,601
    103
    296
    Good news, thanks for the update.:)
     
  8. tourbox

    tourbox Senior Member

    1,311
    68
    54
    Glad your back to charging. Thanks for the update.
    tourbox
     
  9. Jack Klarich

    Jack Klarich Expert Member

    18,544
    153
    399