Zenith Aircraft Builders and Flyers
More Charging Issues
I have 912ULS on a Zenith Cruzer that is 5 years old and 450+ Hrs. EarthX ETV680C battery.
Charles had a 5/29/19 post in this forum about a charging issue problem. He swapped out the voltage regulator with a new one and solved the issue.
About two weeks ago my amp readings started to bounce around from - 2A to + 8A. Previously, the normal was zero amp reading and 13.9 battery voltage. The -2A is the normal when engine not running.
Most recently, on a one-hour flight, it was a steady -2A with a slow battery voltage drop. I'm thinking a voltage regulator issue.
Any other ideas?
Jay
Matt Pope
This troubleshooting guide seems pretty comprehensive and easy to understand: https://pointsforpilots.blogspot.com/2012/12/testing-rotax-912914-g...
Oct 31, 2025
Stuart Brooks
one thing to try before replacing it is to check that the regulator is grounded correctly with a dedicated wire from the regulator case to your main grounding point. A bad ground connection could cause the symptoms you are experiencing.
Nov 13, 2025
Jay M. Johnson
After trouble-shooting using the guide mentioned by Matt and talking to locals who have Rotax engines, decided to replace the voltage regulator. Same issue, -2A discharge. More trouble-shooting and found a heavily corroded inline fuse between the capacitor and the ammeter shunt. Replaced fuse and ran-up engine. Problem solved, I think. Volts and amps are acting like they should. Weather too poor to go flying to test in the air.
on Thursday