Alternator or regulator failure?

[Mike McD]

HI,
I'm having problems with my electrical system...not charging the battery. The battery was replaced as well as the regulator and still having problems...charges the battery for a short time then fails. My A&P called the manufacturer of the alternator and they said there was nothing to fail in the unit..must be something else. Any ideas would be appreciated!
Thanks, Mike

[Andy]

My A&P called the manufacturer of the alternator and they said there was nothing to fail in the unit..must be something else.

Well if your A&P thinks there is nothing in an alternator that can fail you should be looking for a different A&P!

I don't know which alternator you have. The Denso alternator used on the FX-3 has an internal regulator and there are multiple possible internal failure modes. There is also the possibility of an external failure that results in no field excitation.

If you doubt the alternator then take it off and take it to an autoparts store. Many of them have alternator test capability.

[Pete D]

Hi Mike, do you have a CC11-100 Sport Cub? Those run a externally regulated alternator.

Review SB00023 available from the publications button on the Service & Support page. This addresses the three fuses on the alternator output, cabin side of the firewall, upper left side, near the regulator. If there is an issue with the fuse holder or fuse that may explain why changing the regulator didn't fix the issue.

https://cubcrafters.com/c/publications/

Also, with this alternator on the Sport Cub it typically doesn't put out full voltage until you are around 1800 RPM or higher so if you have all the lights, radios etc on while taxing the battery won't be charging. Reduce your load (strobe lights etc) off until you get to the hold short, then turn all the lights on just prior to takeoff.

Feel free to give me a call if you have any other questions and I would be happy to help you. 509-248-9491

[Mike McD]

Pete,
Super helpful...I will show this to my A&P. I remember him talking about it before. I will call if I have any questions. Don't like to be stuck on the ground!
Thanks, Mike

[Mike McD]

Thanks for you reply Andy...gonna start with a new regulator and see if thats the fix.

[Mike McD]

Ok so my A&P replaced the regulator with a new one from B&C...it's working but the amps readout on the Dynon are jumping all over the place. Any ideas?
Thanks, Mike