Fixing the 50DN alternator voltage regulator on our new bus

On a 50DN alternator, poor voltage regulation is a common problem. We purchased this bus knowing that it was doing this, and the prior owner had already spent a lot of time and money working on the issue - including replacing the alternator and going through a few voltage regulators. Yes there is a modern voltage regulator available for the big 50DN alternator we use it in this video. I went through a series of hypothesis about what was causing the issue and tested them, including removing the house batteries, removing the group 31 batteries and trying 8D’s, looking for a bad ground between the engine and the bus body, trying to understand modifications done to the stock wiring over it’s lifetime, and completely bypassing the bus wiring and using new wires between the regulator and the alternator.

The new, temporary wires I was using for testing didn’t do me any favors. Short wires of appropriate gauge, directly and firmly connected are needed. Extra distance or crusty wires will interfere with the signal and add latency - the scope shows this - and interfere with proper regulation.

This is the scope I bought super happy with it, there are many similar. https://amzn.to/3PSbTZz (affiliate link, but purchased and used for a couple years)