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On a flight, I suspect after a good landing bump training a student the generator light comes on. Voltage goes from 13.5 to 12.5 and we drained the battery during that flight to about 11.7 by the end of flight with heating gear etc. Obviously the generator was not charging (generator warning light on).

Double checked the accuracy of the voltage reading on the battery with a Fluke voltage calibration (used the Fluke throughout troubleshooting). First step was to replace the voltage regulator with one that worked. No fix. Double checked voltage regulators on other aircraft and they worked fine. 

Checked the positive continuity from the generator plug to the battery, good with master on, 30 amp fuse ok. Checked all the positive connections at the voltage regulator plug for continuity per Heavy Maintenance manual 74-00-00 figure 74-12.  Checked the generator circuit at the regulator plug both wires-no continuity to ground, generator resistance- low but within specks at the regulator plug .25 ohms while not running, checked the generator output AC voltage while running and about what Rotax Owner video charging trouble shooting observed. 

Put conductive paste (not dielectric bulb stuff) on the regulator plug to assure a good connection.

Just replaced the capacitor with a new one. No fix. 

Everything works but it is not charging. Battery reads 12.5 and can not get it to charge. Somehow I am not getting from the voltage regulator to the battery.  I am out of things I know how to troubleshoot. Any ideas? What could I possibly be missing?

  • Re: No Charging Problem troubleshooting options at a loss now

    by » 5 months ago


    Assuming 912ULS Engine...

    Make all measurements AT the Regulator connector with the connector attached.

    Confirm...

    Engine Stopped, Master ON;  ~12.6v on Regulator R, B+ and C (Relative to Regulator Body, Not Airframe Ground.)

    Engine Running; measure AC Voltage from G to G',  Not G to Ground. ~20Vac

    - - -

    The devil is in the details, Just humor me and do it again. smile

     


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Bill.Hertzel@Yahoo.com
    Clicking the "Thank You" is Always Appreciated.


    Thank you said by: Andrew Dunning, Paul Hamilton

  • Re: No Charging Problem troubleshooting options at a loss now

    by » 5 months ago


    Thanks Bill yes 912 80 hp. I would not ask if I did not want any advise. I did measure the AC voltage from the two yellow leads not to ground. Good idea measuring at the plug, plugged in to regulator while running, I guess I can go in at the back of the plug while plugged in. One thing I did not do. 

     

     


  • Re: No Charging Problem troubleshooting options at a loss now

    by » 5 months ago


    Have you tried sticking a different battery in and observing charging behavior?

     


    Thank you said by: Paul Hamilton

  • Re: No Charging Problem troubleshooting options at a loss now

    by » 5 months ago


    Problem solved but not a typical situation. Went in and checked the parameters with the engine running AND the plug plugged into the voltage regulator. Battery voltage no charging. Checked the AC voltage into the plug. Very low. Hmmm. It was fine not hooked to the plug and running. Pulled the plug off and rechecked the resistance. Nothing. How could this be we checked it before and it was fine. Started up to check the AC out and very low, 1 to 3 volts. Again how can this happen I checked it before and it was ok. Followed the white (hint) generator wires back and found some connectors to the yellow wires. Connectors were burned/over heated. Upon inspection the white wires from the yellow wires to the plug were MUCH thinner, maybe 20 gage verses the 14 gage yellow wires. Hard to believe but someone undersized the wires. Replaced with similar gage wires and problem solved. Hopefully any body should know not to splice wires with thinner wires but it happened.

     



  • Re: No Charging Problem troubleshooting options at a loss now

    by » 4 months ago


    Ken Ryan wrote:

    Have you tried sticking a different battery in and observing charging behavior?

     

    Went through the similar trouble shooting with charging on another aircraft everything was fine except the output voltage from the regulator. We got a new battery and it was normal. So your suggestion Ken did work on another charging problem. However, I do not understand if the regulator is supposed to be putting out 13.6 or so volts, why the bad battery would not allow this? But it does from what I saw? Anyone know why? 


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