I posted this in the general construction forum... and one person answered suggesting I bring it to this forum... so again... any suggestions or information would be much appreciated.

I searched this whole site for the answer, but surprisingly it doesn't look like it's ever been asked. My father-in-law bought an older Mobile Home and is giving it an almost complete overhaul. He asked me for my "input/ideas" for the best way to run wiring between the ceiling and the outside of the unit??

Currently, it is wired so that when he enters the 2 bedrooms and flips the switch, it makes one of the outlets hot...He wants to have a light fixture or ceiling fan in the center of the ceiling that is hard wired and connects to that switch.

He has removed walls the previous owner added in to make a 2 bedroom place into 4 bedrooms, and has repaired all the drywall and applied texture...which I'm sure, if need be we could make a few small holes to run wires thru the walls, and repair it...but the big dilemma is how to get it from the top of the wall to the middle of the room where the fixture will be?

There are heating/AC ducts up there...not to run any wire inside them, I think that would cause temp extremes on the wires as well as create leaks going in and out of the ductwork. But it the best way to follow along the outside of the ducts? The ceiling is not the removable panel type. If you cut into it, it is totally noticeable. Does anyone have any experience in this area and have any good suggestions for me??

Anything would help!

Not sure exact construction, Find a place where you want light(s), Feel with hand, or use stud finder to find side of ceiling truss, 2 X 2, or whatever you can secure box to, Arlington makes around plastic box that will straddle 1 1/2, or 3 1/2 in wood(2 X 4, 2 X 2).
Cut out for box you are going to use, Look and see if you could cut another hole for a smoke detector near switch location in ceiling. This will cover hole, and hopefully help in fishing wires through ceiling, cut light opening first to verify where you can fish to.Might as well hook up power to detector.

If you have a wire locator. You could put signal on neutral, and check for pressence of wiring in ceiling. No slack in wires will make it tough. Pigtails?
If able to get power to light, from another direction, you could do that, and get a wireless X 10 switch, and you can Place on any wall. Can be hand held.

By wire locater you mean what? I was at Home Depot today and the electric guy said nothing they sell at that store would be able to detect wires behind a panel, a stud, or drywall and plaster. He said maybe they sell something like that at an electronic store, but not there.

Assuming I do find there happen to be wires running through the center of the ceiling... Would you suggest a lighting fixture with the standard ceiling box that hangs down from the ceiling OR would Can Lighting/Recessed lighting to be a better (or easier install) fit for a Mobile Home?

Don't think enough room for Cans, If so use the "Remodel Cans" All woork can be done through hole cut for lite.
Progressive Electronics makes a 2 piece locator, consisting of signal generator and a receiver/ with probe that hangs down or you can hold in hand, You actually look for "Null"(Minimum signal) to locate, then at 45 degrees to determine depth.
A Couple of years ago I paid($180-$280?) Very handy, I would look on Ebay or online auction site. I will get model #, and post back here.
How much room in ceiling. Once you cut hole for light. Put digital camera and take pictures.
I have an Easy Share with 2 cables, One allows downloading to computer, the other plugs
Into TV's Composite input(Yellow -Video)Very good set of eyes.

Wow! That camera idea is a great one... I never even thought of that. I have a Canon that has all those ports too! As a matter of fact... I also have a Canon video camera also eith all those ports... but it also has night vision and infrared that can record images in zero light. THat may come in handy... hmmm.

He hasn't actually cut any holes in the ceiling for lights yet... There were so many other things that took precedence, but in actuality... when he asked my opinion about running the wires to the switch... he kind of said, "What do you think would be the easiest way to...and then you can come over and do it." I think if he has a choice, he'd prefer someone else do the electrical work.

The man IS almost 80 years old, and although he has all his faculties (debatable), he isn't as agile as he once was. Speaking of holes in the ceiling, he does have the grill off a few of the air vents. Without actually measuring, they looked to be between 6-8 inches high and roughly 10 inches wide. Those ducts sit between the ceiling and the roofing material, so I figured with that much room, a can light or some kind of recessed housing would fit up there. Do you need more than that depth to get recessed lighting in?

Yes please post the Brand and model# of that contraption you mentioned. I'm sure I will use it quite a bit for this project (at least 3 rooms he wants ceiling lites connected to the wall switches) but it seems the more I do at my own home, the family starts asking for help, then the friends... it never stops.

Its also great for locating where a empty conduit comes from the panel, Very handy.
It is a Progressive 508E Wire Finder, individually the receiver is 500 MT, the transmitter is a 508T. Only make holes where needed, Locate where you would like them, determin e which way you may have to shift because of framing. You may find it easier to fish to a closet, go underneath, across, and then UP to switch, the corner at top can be tough. That is where a detector may need to be installed.

You want "Remodel Cans", cut circle in drywall, fish wires through hole. Hole needs to be correct size, has 4 spring clips. I believe they may need 5 1/2" inches minimum.