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charging system issues

Discussion in 'The Garage' started by Jack Dunneisen, Jan 11, 2017.

  1. I have an 81 heritage special I turned into a chop and have been having issues with it charging, it seems intermittent because one day I can ride it with no issue and the next it will die a block from home. battery will be dead as if it isn't charging, with a multi meter on the battery and revving it there is no charge, I made the harness using a tc bros harness modified to what I needed, Im fairly well versed in electrical diag and theory being a ford technician by trade but this has me stumped, I tested the rotor between the slip rings and have 5.5 ohms I checked between them and ground and its OL so that checks ok, I checked the resistance between any combination of the white wires coming from the stator and they are all .5 ohms so that's good from what I have read, I have checked the resistance of the wires to the brushes and they are all good, I have not checked the output of the whites while running because its cold and I don't have heat in the shop and the battery is dead now from the lack of charge this summer. but as far as I can tell those components are all good, checked the ground from the engine case to the frame and have .5 ohms at either battery neg or the ground post on the frame the only thing I noticed is when you check the resistance between the nut that holds rotor on and ground I have 1.6 ohms not sure why maybe someone could fill me in there, also between the whites and ground I have a very high resistance reading so that also from my research says it is good. any insight here would be greatly appreciated. I do have new brushes as well.
     
  2. Most likely the rotor is not making a strong magnetic field. That may be due to the regulator part of the rec/reg unit not working.
    You will have to start with a fully charged battery, so either charge it up with a bench charger, or buy a new battery if the one you have is dead, as in it fails a load test..
    A simple way to test for a strong magnetic field is to use a 0.003" feeler gauge. Remove the alternator small cover. Hold the feeler gauge 3/4" from the rotor nut. Turn the key on, and the gauge should smartly pull over to the nut. If it does then the magnetic field is normal.

    If the gauge does not pull over, then you can try to bypass the regulator. Have a second person hold the feeler gauge at the same 3/4" from the rotor nut. Now, use a jumper wire from a good bare metal frame ground or from battery negative, and touch the jumper wire to the left outer brush terminal. If the feeler gauge pull smartly to the nut, then that means the regulator has failed and you need a new one. Another possibility that might look like a failed regulator, is if the rec/reg unit is not grounded to the frame. Make sure the regulator has a good ground.

    If your slip rings are not clean, be sure to clean them with some fine emery paper.
     
  3. hey thanks for the quick response I will try that tonight and update this. as far as the ground for the regulator I did check that from the heat sink side to the ground post and or the battery neg and it had close to 0 ohms something like .1 or ,2 if I remember correctly. so I wouldn't think that would be the issue. as far as the reg/rec is there anything I could have done in the build that could have caused it to fail. it started to do this 2 summers ago when one day it just quit and from then on like I said it just seems to do it at random, that being said I don't have a voltage gauge so I don't know if its always not charging or if it is and just is weak charge.
     
  4. On these old bikes, a voltmeter is a "must have". You soon get used to what a normal voltage is, which means you can easily notice when the voltage starts to drop off, and gives you advance warning. I prefer an analog voltmeter, but many others use digital.
    I also have a voltmeter in my car.
    IMG_6230 R1.JPG
     
  5. gggGary

    gggGary You rang????

    Where is regulator rectifier? If you have it stuck inside a can to "neaten things up" that's a good reason for one to fail but we are seeing some old age failures on the 80-84 solid state regulators, there are $100 plug in replacements and simple DIY replacements for less than $25 that are every bit as good. jumping the - brush to ground should make it go "full charge" while running, a pretty good pass fail test that the regulator rectifier has failed. Don't do that for more than a few seconds, you can cook the battery and other electronic$ pretty quick.
    PS always fully charge the battery before doing tests. I think Ford may mention that also.
     
  6. yeah they do say that. that's why I didn't do any live tests just resistance since it all had to be isolated any way. as far as my placement it is mounted to the down tube of the frame opposite the rear engine mount. so I wouldn't think lack of air flow would cause any issues as its more in the open than it would be from the factory.
     
  7. update so last night I put everything back together and used one of my optima car batteries as the one for the bike is dead and I didn't want to wait around for a day for it to trickle charge. with it all together I did the test on the rotor with the feeler gauge and it snaps right over to it from about 3/4 inch away, it did have some residual magnetic pull after the ignition was off, im not sure if that's normal or not but do you guys think it could have been simply a matter of a mix between the brushes I changed because they were at the wear limit and a bad battery ? the battery in it is a smaller size but should have been big enough to run what I have ( no lights besides head and tail and brake, not even high beam as I don't ride it at night) the battery wasn't 100% when I started it after replacing the brushes it was probably in the 11-11.5V range Im guessing that isn't enough. im thinking I may have ruined this one too. being a rigid seems to be taking its toll on my batteries as this is the second in 2 years Im going to have to figure out a better way to mount it on some rubber or something as of now it sits on 3/4 inch foam on the frame and is strapped down with a modified leather belt. also could heat be a factor as it is winter and everything is cold things are making a better connection ? I will rig up some jumper cables so I can run it off the car battery and see if having a full 12.8 volts makes the difference. also noticed with key on my voltage to my inner brush is around 10.5 ish and at the battery its 12.8 that a sign ofa bad regulator?
     
  8. 12.8 at the battery and 10.5 at the brushes is normal. The voltage drop means that normal current is flowing. The normal current of about 2 to 2.3 amps is what caused the strong magnetic field, which caused the feeler gauge to snap right over to the rotor nut.
    Yes some residual magnetism is OK.
    Your previous brushes being at the wear limit, means your alternator has not been charging for quite a while. Compounding the poor charging, is the use of a small battery. If you have been taking only short trips also means the battery never gets a chance to fully charge.

    Your rec/reg unit seems to be working to supply the field current to the rotor. However, the real test is to start the engine and rev the rpms up to 3000+. Do this with the headlight on. You should see 14 to 14.5 volts if things are working correctly.

    2 suggestions. Use a 14 amp/hr battery and install a permanent voltmeter on your bike.
    Small batteries just cause problems on these bikes.
     
    littlebill31 likes this.
  9. hey thanks for the advice, as I said before I have far more experience in the automotive world and specifically late model stuff so these bikes are a constant learning adventure. but I wouldn't trade it for any other hobby, Im just glad there is a great community here willing to help when they can.
     
    gggGary and jussumguy like this.

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