Greetings - and Thank You in advance for your answers, comments, and suggestions.

One of the early upgrades I made to my coach was elimination of the buzz box and replacement with a Progressive Dynamics PD60. All good.

The PD60 is plugged into a 12VAC receptacle in the electrical cabinet. I've always thought that while running my generator (Onan 4K) - the PD60 was powered up and charging the (house) batteries. (The factory isolator is still connected as is a Yadina combiner - per Gene Fisher's circuit diagrams.)

I visited the coach at the storage yard this evening and started the generator and the engine as I do about once a week. After the engine came to temperature - I shut it down and had just the generator running. Everything looked just fine... 14V or so on the house 12V circuits - indicating that some charging was taking place. I don't know why - but something possessed me to unplug the PD60 and see what would be affected... Surprise !! Still 14V or so on the house circuits.
If there was no load on the house circuits, they were still trying to circulate the electrolyte and make use of the 14.2 charge voltage of the PD.

So... it occurred to me that the Onan Flywheel Alternator is still connected and putting out DC voltage !
If you have a box-stock 73-23, the Onan charger is not connected to the house bank and only does a half hearted job of keeping up the dedicated battery in the back.

A couple of questions arise:

My gut tells me that the PD60 is a better battery charger than the flywheel alternator... correct ??
That is Correct.

When running the Onan with the PD60 plugged in - who's charging the batteries - flywheel or PD60 or both ??
The flywheel alternator can only contribute a few amps at best, but it won't upset the PD9260.

If it's both - I'm really not getting the advantage of the PD60 battery charging intelligence am I ??
You will have to run the generator more than about 4 hours before the PD will start to think about backing off, so don't worry about it. More down the page.

Did anything get damaged while running both ??
Not likely.

Which is preferable ?
The PD will do you more good in lots of ways.

It's pretty common for me to drive with the Onan running and the rooftop AC blowing...
You and more than a few others.

Steve W
1973 23'
Southern California

So... it occurred to me that the Onan Flywheel Alternator is still connected and putting out DC voltage!

A couple of questions arise:
My gut tells me that the PD60 is a better battery charger than the flywheel alternator... correct ??

When running the Onan with the PD60 plugged in - who's charging the batteries - flywheel or PD60 or both??

If it's both - I'm really not getting the advantage of the PD60 battery charging intelligence am I??

Did anything get damaged while running both ??

Which is preferable?

It's pretty common for me to drive with the Onan running and the rooftop AC blowing...

The important thing is to read and follow Duane's instructions. The two'fer needs to stay connecting the 2 terminals taped up but be off of the regulator. Disconnecting and taping the other wire prevents the parasitic drain possibility.

True. But in the interest of remembering Duane you wrap it with tape like he did in the DVD. I think his thinking was that way you could undo and restore easilly. Actally even good e tape like Scotch 33 is only good about a year in "underhood environs". You really need the stretch type underhood loom tape.