boom3
Well Known Member
Long?
I have about 375 hours now on my RV-7A since new. My alternator is a B & C 60amp with the LR3C-14 voltage regulator. To date it has never missed a beat. Recently after a local flight while on downwind to land at my airport I notice my low voltage light flashing. (Something I?d never seen in flight) I checked my 5amp circuit breaker, which wasn?t tripped, and tried cycling my alternator field switch. No Change. After landing I pulled out my POH so I could identify and check the fuse. (My field circuit starts out with and automotive style ATC fuse then is wired through a Potter and Brumfield 5A circuit breaker, then through the master switch, alternator switch, then is connected to the LR3C-14.) I found that my 5A fuse was blown. I went ahead and replaced the fuse and started the engine again. It blew right away. OK well it?s trying to tell me something so I pulled it the hanger and went home for the evening.
On my next trip to the airport I started digging into it. Everything looked good and I couldn?t find any reason for it to be tripping. I followed B & C?s troubleshooting guide and verified all the voltages and resistances were correct. I also followed all the wires and checked for chaffing, grounding, or poor connections. Finding nothing I put in another fuse and pulled it outside and started it up. Everything was good and I was indicating a steady 14.4 volts. I turned it off, preflighted, and started it again with no issues. No issues during the runup either so I decided to take it up for another short local flight. Stronger winds aloft over the Cascades provided some light turbulence here and there but the voltage remained rock steady. I flew it around the airport environment for about an hour with no issues. However upon reducing power on downwind it popped again. OK something is really up. Out of time I put it away again.
I did some research on VAF and read about some possible culprits. I read about problems with the field connections on the alternator itself not making good contact, bad master switches, bad alternator switches, and bad circuit breakers. I also called B & C who were great and very willing to help. I emailed them my troubleshooting checklist and we talked about everything. They were pretty convinced it was something with the wiring and mentioned most of the same things I?d read about on VAF. They really stand behind their products and said they should not have a problem making TBO. They said that most, like 98 percent, of all problems end up being a bad connection somewhere in the wiring.
My next opportunity several days later I decided to really tear into it. I replaced the master switch, alternator switch, bypassed the circuit breaker (still kept the fuse), and followed every wire. I disconnected every single connection, checked the crimps and re-crimped for good measure. Everything looked great. I even removed the plastic alternator connector from the plane and took to it to the bench where I could give each conductor a good tug and meter for any changes in resistance. Although not avionics, my whole career has been in the electronics / low voltage field so I was pretty confident with my wiring. I?m definitely not perfect though so it was nice to physically verify everything again. 100% confident in the wiring I put it back together again and pulled it outside to start it. The fuse blew again right away. Dang! Well that leaves the alternator or the regulator itself, but which is it? I drove home wondering what to do next.
I called B & C again the next day and they really couldn?t offer much more help. If all the voltages and resistances are reading correctly it should work fine. The Odyssey battery crossed my mind as I thought I read about that being a possibility.
On the weekend I got the bright idea to run up to the hangar and remove both the alternator and voltage regulator and bring them home. At home I mounted everything to a board and rewired everything from scratch. I have an old drill press with a 1/3hp motor with a pulley that would provide the alternator adequate RPM. Upon powering it up the battery would start to charge for about 5 seconds and then the fuse would blow. Watching my digital VOM meter closely, it would settle down about 14.4V then suddenly climb to above 15V before blowing the fuse. It appears the LR3C-14?s crowbar overvoltage circuit was doing its job and blowing the fuse.
Things setup at home. (field fuse not installed in this picture)
I made another call to B & C and they agreed it was voltage regulator causing the problem and not the alternator. Although not happy about buying another voltage regulator, I was ecstatic about finally finding the problem. I ordered a new one from Aircraft Spruce West and was able to get everything re-installed Thursday evening. Although dark, I needed fuel so I fired it up and taxied to the pumps to try it out. I loaded it up pretty good with pretty much every light on and the voltage stayed nice and steady. Another start and the taxi back to the hangar was the same, everything was great.
On Friday, during daylight, I was able to fly it again after work. I flew around the airport awhile, turning on and off landing lights, varying RPM, etc and everything was perfect. I ended up flying it for a couple hours with several landings. I?m confident it?s fixed!!! Ok now where was I. Oh ya, waiting for decent flying weather again.
Some things I learned...
B & C is a great company to deal with.
Even a 7.5A ATC style fuse will still blow before the 5A circuit breaker. When I find one, I will replace it with a 7.5A slow blow.
Although 98 percent of the problems are caused by wiring or connections, that isn?t always the case.
Part of me wishes I?d just pulled everything out of the plane at the beginning, but it would suck to do all that and then find a simple bad connection somewhere.
I have about 375 hours now on my RV-7A since new. My alternator is a B & C 60amp with the LR3C-14 voltage regulator. To date it has never missed a beat. Recently after a local flight while on downwind to land at my airport I notice my low voltage light flashing. (Something I?d never seen in flight) I checked my 5amp circuit breaker, which wasn?t tripped, and tried cycling my alternator field switch. No Change. After landing I pulled out my POH so I could identify and check the fuse. (My field circuit starts out with and automotive style ATC fuse then is wired through a Potter and Brumfield 5A circuit breaker, then through the master switch, alternator switch, then is connected to the LR3C-14.) I found that my 5A fuse was blown. I went ahead and replaced the fuse and started the engine again. It blew right away. OK well it?s trying to tell me something so I pulled it the hanger and went home for the evening.
On my next trip to the airport I started digging into it. Everything looked good and I couldn?t find any reason for it to be tripping. I followed B & C?s troubleshooting guide and verified all the voltages and resistances were correct. I also followed all the wires and checked for chaffing, grounding, or poor connections. Finding nothing I put in another fuse and pulled it outside and started it up. Everything was good and I was indicating a steady 14.4 volts. I turned it off, preflighted, and started it again with no issues. No issues during the runup either so I decided to take it up for another short local flight. Stronger winds aloft over the Cascades provided some light turbulence here and there but the voltage remained rock steady. I flew it around the airport environment for about an hour with no issues. However upon reducing power on downwind it popped again. OK something is really up. Out of time I put it away again.
I did some research on VAF and read about some possible culprits. I read about problems with the field connections on the alternator itself not making good contact, bad master switches, bad alternator switches, and bad circuit breakers. I also called B & C who were great and very willing to help. I emailed them my troubleshooting checklist and we talked about everything. They were pretty convinced it was something with the wiring and mentioned most of the same things I?d read about on VAF. They really stand behind their products and said they should not have a problem making TBO. They said that most, like 98 percent, of all problems end up being a bad connection somewhere in the wiring.
My next opportunity several days later I decided to really tear into it. I replaced the master switch, alternator switch, bypassed the circuit breaker (still kept the fuse), and followed every wire. I disconnected every single connection, checked the crimps and re-crimped for good measure. Everything looked great. I even removed the plastic alternator connector from the plane and took to it to the bench where I could give each conductor a good tug and meter for any changes in resistance. Although not avionics, my whole career has been in the electronics / low voltage field so I was pretty confident with my wiring. I?m definitely not perfect though so it was nice to physically verify everything again. 100% confident in the wiring I put it back together again and pulled it outside to start it. The fuse blew again right away. Dang! Well that leaves the alternator or the regulator itself, but which is it? I drove home wondering what to do next.
I called B & C again the next day and they really couldn?t offer much more help. If all the voltages and resistances are reading correctly it should work fine. The Odyssey battery crossed my mind as I thought I read about that being a possibility.
On the weekend I got the bright idea to run up to the hangar and remove both the alternator and voltage regulator and bring them home. At home I mounted everything to a board and rewired everything from scratch. I have an old drill press with a 1/3hp motor with a pulley that would provide the alternator adequate RPM. Upon powering it up the battery would start to charge for about 5 seconds and then the fuse would blow. Watching my digital VOM meter closely, it would settle down about 14.4V then suddenly climb to above 15V before blowing the fuse. It appears the LR3C-14?s crowbar overvoltage circuit was doing its job and blowing the fuse.
Things setup at home. (field fuse not installed in this picture)
I made another call to B & C and they agreed it was voltage regulator causing the problem and not the alternator. Although not happy about buying another voltage regulator, I was ecstatic about finally finding the problem. I ordered a new one from Aircraft Spruce West and was able to get everything re-installed Thursday evening. Although dark, I needed fuel so I fired it up and taxied to the pumps to try it out. I loaded it up pretty good with pretty much every light on and the voltage stayed nice and steady. Another start and the taxi back to the hangar was the same, everything was great.
On Friday, during daylight, I was able to fly it again after work. I flew around the airport awhile, turning on and off landing lights, varying RPM, etc and everything was perfect. I ended up flying it for a couple hours with several landings. I?m confident it?s fixed!!! Ok now where was I. Oh ya, waiting for decent flying weather again.
Some things I learned...
B & C is a great company to deal with.
Even a 7.5A ATC style fuse will still blow before the 5A circuit breaker. When I find one, I will replace it with a 7.5A slow blow.
Although 98 percent of the problems are caused by wiring or connections, that isn?t always the case.
Part of me wishes I?d just pulled everything out of the plane at the beginning, but it would suck to do all that and then find a simple bad connection somewhere.
