7pilot
Well Known Member
On a recent flight the field breaker for my alternator popped in flight. I attempted to reset it and that didn't work. I shut down most of my electronics and tried again to no avail. I elected to point the nose toward home and go sort things out. For some reason, while in the pattern at a reduced power setting I reached over and tried to reset it again. This time it reset and the alternator started charging normally. I landed anyway, deciding this needed further trouble-shooting. I was able to reproduce the failure when I did a high rpm run up on the ramp, but as long as I kept my engine below about 2000 RPM all charged normally.
I suspected this was caused by the Alternator Control Unit (Combined regulator and over-voltage). I called B&C described the problem, since I have their ACU and Alternator, and they suggested that it sounded like a loose wire. I was unconvinced but went back to the hangar to run the wires again and check the plug on the alternator as they recommended. All appeared tight and I ran the engine again just to confirm that I still had the issue after fiddling. Now I was running close to the time for a trip from the DFW area to CLT and instead of wasting more time waiting for someone to call me back about my issue I called to order a new ACU and have it overnighted. They told me they had one rebuilt that they could send for half the price and have it to me the next day - I was happy to get the price break and ordered the part.
After installation of the rebuilt ACU I did a test flight - all checked out normal. So I departed on my flight to Charlotte and arrived without further incident a little over 4 hours later (gotta love those tailwinds at 15,500!!)
I attended my grandson's 3rd birthday party and departed the next day. Flew to Atlanta to see my son, still all is well. Departed Atlanta enroute to my fuel stop I suddenly lost all charging - however the field breaker did not pop. Still nearly 3 hours from home, I shut down most of the electrical and continued toward my fuel stop that was about 45 minutes away. About 20 minutes later, suddenly my alternator comes back on line and begins charging again. This lasts almost to the point of landing when the system quit again. I made a quick fuel turn since I wanted to ensure I didn't have to fly any at night with my degraded system. On takeoff I again had a fully operational system. The system continued to operate on and off in 20 to 30 minute intervals all the way home.
I pulled the cowl and began the tests provided with the ACU. The test that checks for a lower voltage than bus voltage coming out of the field of the alternator failed - until I touched or moved something. Now, mind you, this is a test that looks for a lower voltage and I was getting a higher voltage that the test sheet says indicates a potential open in the alternator field to ground circuit - in other words I was reading normal bus voltage when I should have been reading 1.2 volts less. Since the failure suddenly went away I ran the engine again - it initially charged and then quit again. I shut down and got the same test results as the first time - initially failing the same test and then passing. Sounds like a loose wire? I checked them all carefully with a meter on them while I was moving them. Checked for continuity on the field wire, etc, etc...
I am at a loss why the problem would continually disappear and then come back...Bad Alternator? Could I have weakened/damaged it in trying to reset during the initial problem? Bad ACU rebuild? All other ACU tests pass.
I called B&C and they are at SnF - so no help this week - I want to get back in the air!!
If you have some experience with this, I would appreciate your thoughts.
Thanks! Stewart
I suspected this was caused by the Alternator Control Unit (Combined regulator and over-voltage). I called B&C described the problem, since I have their ACU and Alternator, and they suggested that it sounded like a loose wire. I was unconvinced but went back to the hangar to run the wires again and check the plug on the alternator as they recommended. All appeared tight and I ran the engine again just to confirm that I still had the issue after fiddling. Now I was running close to the time for a trip from the DFW area to CLT and instead of wasting more time waiting for someone to call me back about my issue I called to order a new ACU and have it overnighted. They told me they had one rebuilt that they could send for half the price and have it to me the next day - I was happy to get the price break and ordered the part.
After installation of the rebuilt ACU I did a test flight - all checked out normal. So I departed on my flight to Charlotte and arrived without further incident a little over 4 hours later (gotta love those tailwinds at 15,500!!)
I attended my grandson's 3rd birthday party and departed the next day. Flew to Atlanta to see my son, still all is well. Departed Atlanta enroute to my fuel stop I suddenly lost all charging - however the field breaker did not pop. Still nearly 3 hours from home, I shut down most of the electrical and continued toward my fuel stop that was about 45 minutes away. About 20 minutes later, suddenly my alternator comes back on line and begins charging again. This lasts almost to the point of landing when the system quit again. I made a quick fuel turn since I wanted to ensure I didn't have to fly any at night with my degraded system. On takeoff I again had a fully operational system. The system continued to operate on and off in 20 to 30 minute intervals all the way home.I pulled the cowl and began the tests provided with the ACU. The test that checks for a lower voltage than bus voltage coming out of the field of the alternator failed - until I touched or moved something. Now, mind you, this is a test that looks for a lower voltage and I was getting a higher voltage that the test sheet says indicates a potential open in the alternator field to ground circuit - in other words I was reading normal bus voltage when I should have been reading 1.2 volts less. Since the failure suddenly went away I ran the engine again - it initially charged and then quit again. I shut down and got the same test results as the first time - initially failing the same test and then passing. Sounds like a loose wire? I checked them all carefully with a meter on them while I was moving them. Checked for continuity on the field wire, etc, etc...
I am at a loss why the problem would continually disappear and then come back
...Bad Alternator? Could I have weakened/damaged it in trying to reset during the initial problem? Bad ACU rebuild? All other ACU tests pass.I called B&C and they are at SnF - so no help this week - I want to get back in the air!!
If you have some experience with this, I would appreciate your thoughts.
Thanks! Stewart
