02-26-2003 Ask Mike! Archive
Lights and amperage issues

I just read the generator question on the web site. I have a C-35 with an alternator. If I turn on both taxi and landing lights, the voltage will go below straight up on the ammeter and reset the JPI and the ADF. The battery is new (this seems to have helped a bit). What next? Lower amperage lights?

Thanks. -Jim


Jim;

Sounds to be a rather severe draw. You didn't mention what RPM range this does that, so I'll go under the impression it's all the time. I'll also go with the impression the alternator has a clean bill of health.

When turning on the lights, do them one at a time, try to avoid actuating both switches at once. Combined, the (stock) landing lights are the biggest draw on the electrical system in a Bonanza. Check them one at a time, watching the ammeter and confirm this with the voltmeter in the JPI. You might find one of them has considerable more negative effect on the system. If that's true, check to see if it has the correct lamp installed. Also, check connections in wing root (requires I/B gear doors open) for a partially worn thru insulator. These are the easy checks, you may need to dig in further to find the offending problem.

The circuit breaker should also be checked for proper amperage. If it's incorrect (too high) or inoperative, it wouldn't relieve the system from a short to ground, as it sounds like you may have.

I certainly recommend the STC'd lower amperage lights, but in this case there is another problem; lamp change would only be a band-aid.

Gear Green,
Mike