some light on odd electric issue

[mbodak]

thank you so much for that insight...my wife and i do appreciate an informed source helping us understand our 337 issue..we have owned this same 337 for 12 years now....could you please explain the run/stby system a little.....when this odd electric issue, of no charging of our battery, would show itself...we could, by selecting "stby", establish charging again but.. only if we turned the master switch off too...

[Pete Somers]

If the regulator drops off line and both alternators stop charging the battery, you would first select the other regulator or to restore the system 1. Master switch off, 2. RUN/STBY to STBY this will restore the electrics. The reason you have to select Master off on your 337 is that there are diodes in the system that block the STBY system when in normal mode, however with the Master off and the switch in STBY current from the battery will flow through the diodes to the field, allowing both alternators on line with the Master off, turning the Master back on will restore the charging system to the battery.
This is a alternator restart system which allows you to restore the charging system in event of a flat battery.

This is a big clue to your charging problem, if you cannot restore the system by selecting the other regulator, then it has to be that you lose power to both regulators and the common parts are the bus bar, circuit breaker, or wiring. Should not take much finding.

Regards
Pete

[mbodak]

thanks again for shedding light on our skymaster...we think it is a wonderful aircraft and your insight is truly apperciated...we will advz what the a&p's do and how it works

[stackj]

Mbodak

See your original post too. I have posted some information there as well as given a reference for a wiring diagram that may be easier to read than the one in the manual.