AC-DC switch in 1961 AS

[Studioman]

Technical question on my 1961 AS.
This is the switch inches away from the back roof-vent.
I assumed it to be a choice between AC or DC, with the middle being "off".. (Originally I assumed it was for the entire camper lighting, which was not the case)
But the (what appears to be factory) fan motor is AC only.
If you look into the box, you will see a bunk of wire(s) taped together up in the far corner. Could that be DC (I don't want to tear it all apart if there is no chance of it being DC)? I don't believe the little black switch within the vent opening to be factory. Indicating to me someone's messed with it. The motor vent holes line up PERFECTLY with the bracket holes, which is why I believe it to be factory.
It would take me 5 minutes to get the AC fan in and have it operational, but I would prefer to have a new DC fan (Which I already bought) up there.
Generally, the AC fan would work for us and how we normally use the trailer.
I understand I have two fairly simple options on how to get DC to the opening (from the closet or from the rear ceiling cabinet).
Is anyone familiar with what this switch did from the factory (As I said, I believe at least parts of the wiring in the opening have been messed with)?
It seems to me the transformer was to convert the AC to DC? But for what reason if the fan motor is AC only?
Any input, particularly from people who have seen this setup before would be TOTALLY appreciated!!!

[Studioman]

Does anyone at least know if 12v DC should be present in this box?
Thanks!

[overlander63]

When we installed a Fantastic vent in that spot in our '63, we had to run a wire from the 12 volt lights in the bathroom up to that point.

[thiel]

Wait. You have a switch in your trailer that, when activated, plays AC/DC?

That should come standard!

[HiHoAgRV]

From what I recall, the transformer was solely used to drop the 110V AC down to 18(?) volts. The switch selects battery or transformer power to send to the fan. I'm less sure about the motor but it seems it is a AC or DC design.

I do know that without shore power, the AC selection will not work, likewise with no battery or charger, the DC will not work.

On edit. It looks like someone modified yours to back feed the transformer into to DC system for the rest of the trailer(?)

[Studioman]

HiHo,,, GREAT questions,,, neither of which I can answer, and I know the trailer VERY WELL!!!
I have a lot of friends who are also familiar with similar projects who are all at a loss.
I think someone has "messed" with the wiring within that box (the switch box shown above). The little switch just before the fan is the main reason I think it's been some-how "Modified". The Transformer very well may be just dead, or possibly used in reverse within the system. But as of today, EVERY SINGLE AC and DC point works perfect (Even this box has AC present when plugged into shore power (Obviously).
I am going to try to mess with it in the next few days. I'll take some notes as I try to narrow down why there are so many wires with AC present going through them (in the said box).
I could hook up the factory AC fan and have it working within minutes. With a little more effort, I could feed DC to the opening and use the new DC fan I was wanting to use.
ANY OTHER info would be greatly appreciated!!!

[ijustlee]

The junction box is what is called a Re-Work box and you could buy one just like it at a lot of hardware stores. It may or may not have been factory as far as I know but probably came that way. It does seem that the fan motor has brushes and could work on either AC or DC. You could put a bridge rectifier in the low side of the transformer and use your new DC motor.

[ijustlee]

After looking at the bigger photos I still can't see exactly how the wires are hooked up but yes DC should be in that box with the AC. With electricity it is necessary to know exactly what each wire is connected too as guessing is not good enough! That said, I'm guessing that the DC is hooked to one end of the switch in the box and AC from the low volt side of the transformer output is connected to the other side of the switch. The center contacts of the switch in the box go to the fan motor through the other switch to turn the fan on and off. It is considered bad practice to have both 120V AC and 12V DC in the same box so I don't know if the factory would have done this when the trailer was new. A lot of trailers of all brands only had one set of wiring back then and you had to change bulbs when changing from shore power to battery power. With a trailer this old you should trace every wire to be sure you know what is what, anything could have been done over the years! I'd also guess that the transformer was hot all the time or the smaller switch was added to turn the transformer off so you don't hear the hum all the time and the 2 pole double throw center off switch was what switched the fan motor on and off. Hope this isn't confusing but you can't really be sure of old stuff from a photo!