Rear alternator falls off line

[JimC]

If you turn off the front one after the rear drops, does the rear then come alive? If so, I suspect it's a voltage issue and can be fixed with an adjustment.

My 340 (similar setup to the parallel alternators in the 337s) will drop one alternator (usually the high one) if they differ by more than 0.5 volts. Both are working, but it won't parallel until the regulators are adjusted to have them match within 0.5 V. The good news is that it's a no-parts fix - just adjust the output voltage on each one to to match. I have to re-match them to compensate for drift about once a year.

[hharney]

Please reveal the vintage of your 337. There are many variations to these Skymasters and not knowing the model makes it hard to troubleshoot. There are a number of threads about your issue. If you use the SEARCH function above it may help you learn more of the system.

[weebyf15]

Thanks guys; it is a 1979 P337H. I have not actually tried turning the front off while the rear has kicked off line. I will try that next time I get a chance to fly.
Maybe awhile as I also have a bad starter adapter on the front engine. I’ll search the threads as well
Brad “Weeby” Young