picked up a free camper off craigslist so, as you can imagine, it needs some work.
propane stove and furnace fired up with a little cleaning/troubleshooting and now i am going after the lighting.
i am a complete newbie to campers and am trying to understand how a 12v and a 110v lighting system co-exist.
is there a step-down transformer somewhere that converts 110v to 12v ? i can't see one anywhere and i don't understand how the 12v lights could possibly work on 110v power without one. Also, how do the 110v outlets function if voltage IS being stepped-down by a transformer ?

thanks for any help/direction you can provide.

p.s. there is a small breaker box which obviously protects the 110v wiring. can i assume that the 12v wiring is protected by a fuse in the truck itself ?

 

Our former 1977 Security camper had a metal box under the sink that had a rocker switch to choose 12v or 120v,I assume that was the charger as well.

 

At least in my travel trailer, all 12 volt items are powered from the battery. The 120v circuit goes to a converter which the outputs 12v to charge the battery. If you're connected to 120v AC shore power and you have all the lights on then you're discharging and charging the battery at the same time. That's a gross simplification though.

Here's a circuit diagram that's from AirStream

 

Knowing a little more about your camper might help. But, they are all built pretty close to the same with minor differences spread out among year models.

A very basic explanation and generalization is that any camper I have been around runs on 12 volts. The 120 feed is split off to feed the 120 outlets (if equipped) and the 12 volt converter which also charges the battery or batteries. All lights, furnace, fans, water pump...generally are 12 volt. They will be powered from the battery or from the converter depending on how old it is and / or the Make and Model.. My 76 Totem ran straight off the battery. The only thing plugging it in to 120 did was charge the battery.
The 78 King of the Road ran off the converter when plugged in and the converter charging the battery if it sensed the battery below a certain level.
Lance and Alpenlite were/are the same.

The Lance and the Alpenlite both supplied 12 volt from the converter to power all 12 volt needs and charge the battery if over charge protection circuit says its O.K. to charge..
The 97 Lance 880 Legends had a single battery. isolator/kill switch in the battery compartment. The 2005 Alpenlite has two batteries and derives 12 volt power from the generator / 120 power source and then from the battery.. The Alpenlite has an Onan Generator so there are some additional circuits for that. It has a total electrical supply kill switch right by the inverter in the step/bench compartment.
In the 78 King of the road we had, the converter and electrical boxes were under the sink. In the 97 Lance there was a 12 volt fuse box under the sink between the water filter and the water pump, and a few addition fuses along with circuit breakers and converter behind the metal plate with cooling grate in the step cabinet - (Step / bench). The Lance had a total 12 volt electrical kill switch in the battery compartment. In the 2005 Alpenlite Santa Fe Limited, everything, including kill switch is in the Step Cabinet. It also has an access panel to the 'back' side of the electrical compartment that allow access to the electrical control center from the outside.

Since your in rebuild mode, do yourself a little favor and replace the lights with LED's.

Alpenlite inside big access door


Alpenlite Outside Access (Back side of converter and connections.)


Access to Lance Legends 880 Electrical Panel


Lance 880 Control Panel / Converter - 12 volt fuses on circuit board on the right.

Lance 880 12 Volt Fuse Box under sink

 

This is a blow up of the Operation Guide. If you can see it well enough to see C, it explains the converter operation with or without 120 volt. Both the Lance and the Alpenlite operate along these lines. With 120 plugged in, 12 volt lights and motors are operated from the converter and the sensing circuit charges the batteries if needed. I cannot say this operates in identical fashion on all campers.

 

thanks, everyone, for the feedback.

the camper is OLD, probably built well before al gore invented the internet.
for the record, it's a vanguard model p8rf ... built by a local manufacturer in richmond, b.c., canada , so not a word about it on the internet.

today was a case of 1 step forward, 3 steps back. after repairing a bad connection and improving a ground, i got ALL the lighting to work on 12 volts ... yay !
then i plugged in the 120 feed, switched on a light, and POOF ! the bulb blew and, to make matters worse, i no longer have 12 volts anywhere on the system.
it's as if a fuse has blown/breaker tripped but, there is no 12v fuse or breaker that i can find anywhere.
i am having a hard time wrapping my head around this system because the 12 v lighting is wired in with the 120v outlets.
at this point i have to think that the previous owner must have done that in error because even if there IS a transformer (perhaps built onto the the backside of the 120 input on the outside of the camper?) then would it not also be stepping down the 120 going to the receptacles ? that makes no sense. so i think that my next move would be to disconnect the 2 electrical outlets from the 12v lighting ... but i don't know how i am supposed to get my 12 volts back, or why i even lost it in the first place.

 

Under no circumstances would I plug the camper back into a 120v source until I had identified the malfunction and corrected it. 120 current down a wire designed for 12V usually does not end well.
My next move would be to start with the 120 volt supply cord and follow it all the way into the camper to see where it goes and what it is connected into...You may have to get a toner / line tracer to avoid ripping out walls/cabinets or ripping off siding.
https://www.lowes.com/LowesProductCo...m=wiring+toner

I had a converter go bad on me a year ago. (First time it had ever happened to me.). However, I never had any issues with 120 going where it shouldn't. I just lost the ability to charge the battery or to run 12v stuff in the camper off of anything except the batteries. My generator has a 120 plug in on it so I was able to plug the extension cord in and charge the batteries using a conventional automotive battery charger.

 

Reading the post and what bisquit concurred, i could only imagind what that 12v wiring looks like now, throughout the camper, when 120v was applied...being that it was a free camper, id be leaning toward its use to just a weekend warrior and nothing more. Rewire the waterpump for it to work but invest into a few led battery operated switches/stick ons..etc and forgetabout 120v..portable gennie is that answer for your 5am cup of joe or a firepit

 

I sold auto parts back in the old days, and I remember we used to sell 12 volt 50 watt incandescent light bulbs that were identical to regular 120 volt incandescent light bulbs for use in 12 volt trouble lights.

I seem to vaguely recall reading somewhere that on some of the old campers, you had to change the light bulbs when switching from 12 volt dc to 120 volt ac.

I absolutely could be wrong about this. They say the memory is the second thing to go when you get old. (You all know the punchline to THAT old joke!)

Question for the original poster: Are your light bulbs small like automotive taillights, or large like regular household light bulbs?

 

Apparently Google knows way too much about what I'm doing here in the forums. This blog post popped up on my phone, which I don't use to read the forums.

https://axleaddict.com/rvs/RV-Camper...nd-Replacement

 

Optimistic ... your post finally clued me into what is going on here.

there are 5 lights total in this camper; 1 small 12v automotive size bulb over the over-cab sleeping area plus 4 "household incandescent size" bulbs in the kitchen area. there is also a single 12v "cigarette-lighter" style outlet and 2 120v outlets.
2 of the kitchen area bulbs are the 12v 50 watt bulbs you have described, and 2 of them are compact flourescent 120 volt bulbs ... this should have been my first clue, but for some reason i completely ignored it.
the P.O. had actually had things wired correctly, but the 2 12v bulbs installed in 120v receptacles had completely befuddled me. when i eventually plugged in the 120v power and switched one of them on, it blew immediately.

i now understand how this system works ... everything is supposed to operate on the 120v supply EXCEPT the 12v dome light and the 12v outlet (there was probably a 3 way fridge in there as well, but it has been replaced by an ice-box).
i may have fried the 12v side of things but the 120v side should work fine with the proper bulbs installed.

will spend a bit of time on it monday or tuesday and confirm all this, but i am pretty sure i am now on the right track.

thanks to everyone for the help so far !

 

well, dodged a bullet there.
no wires or components fried (other than the 12v bulb), all electrical working except for the 12v car stereo, but that's way down the list of things to do.

next up, replace the water tank which the P.O. said was leaking (he provided a spare tank). it looks like the factory installed the tank and then built around it, so i think i have to cut it apart in the filler neck area in order to remove it.
this is a very simple cold water system ... no hot water and no electric pump; manual pump only.

if you think my electrical skills are weak, stay tuned for the plumbing chapter !

 

Ha! I learned the hard way that Shark Bite fittings are my friend. I keep spares on hand.

 

i had to look up "shark bite fittings". not sure if i am going to need any but good to know they are out there.

did my first real inspection of this fresh water set-up. the sink mounted pump isn't connected to anything so i am thinking that the tank is not the original. there is a schraeder valve outside the camper which forms part of the filler inlet. it seems that you would pressurize the system either with a bicycle pump or , as i just did, with a compressor. having done so, the leak that the p.o. mentioned became readily apparent. it leaks at the weld between the filler neck and the tank itself. i am now thinking that getting someone to weld this (aluminum) tank might be a simpler fix than taking the spare tank provided and trying to make it work.

"free" sure means a lot of work but i am learning a lot about these campers and it's much better to make all my mistakes in the driveway rather than 40 miles from anywhere.