[Edited to add: I see Rooney posted while I was typing, so I hadn't seen his post. Sounds like his rig may be different; but I know of other Chinooks that are done just like mine, so I guess you will have to see how yours is.]
Yes, at least they are on my rig. But from your initial description I wasn't sure if you mean the markers and tails.
So, since you do, here is what I know for my generation of Concourse, as built.
1) Chinook didn't use the usual Ford wiring to power the taillights. Instead, they took the "cutaway and stripped chassis"
trailer light wiring (two wiring connectors provided by Ford) and used one of them (the one that powers the basic trailer functions vs. the "extra" ones) to power the taillights and the marker lights. But wait, there's more...
So, I knew that Chinook had used this "schnozzle" (as I call it because the Ford end connection sort of looks like a periscope) to wire the taillights, because when I got my rig I wired in a new trailer lights connector. For one thing, I like a 7-way style plug (even if not using 7 ways), and for two, I needed one of the additional wires (the reverse light one, to power my trailer's surge brake lockout solenoid). So okay, I crawled under to disconnect the original four-way trailer connector. I had the Ford "camper wiring kit" drawing, so I knew what I was looking for (where the four-way joined the schnozzle). But wait, what are these OTHER wires attached to the trailer wiring schnozzle? And they go up into the Chinook floor...?!?
Long story shorter, yep, Chinook used those wires to power the Ford taillights. Good to know, since it's unconventional. I tucked that away for future reference and finished my trailer wiring job. Trailered many miles with no problems, until...
One night (of course it was at night, since it involved lights), I was towing a cargo trailer and when I turned on my lights as it got dark, I could see they were not lighting up (the trailer lights, some of which I could see in my side mirrors). Huh, when I had hooked up, not three hours before, I had checked all the lights and they were all working perfectly. At just about this time, my buddy who was behind me mentions that I also have no taillights (we had walkie-talkie type radios). Groan.
So we pull into a rest area, and I spend a few hours groveling in the dirt under the Chinook while trucks whizz by inches from my ankles. I knew it must have something to do with how Chinook did that wiring, but it took me awhile to piece it all together. So here is what it turned out to be (a combination of).
1) What I knew already, that Chinook used Ford's trailer wiring schnozzle to power the Chinook taillights.
2) And they ALSO used it to power the Chinook running (marker) lights.
3) The reason this trailer caused a problem was that it had a LOT of lights, and none of them were LED.
4) And the really tricky (and somewhat stupid IMO) part is that Chinook, apparently in an effort to be tidy and logical (that part is good), not only used the Ford trailer towing wiring that Ford ran to the rear of the frame (by the trailer hookup), but they THEN ran a (long, skinny) wire from right back there ALL THE WAY up to the added Chinook
fuse block that's by the driver's left shin (Labeled "Marker Lights" and having a pretty small
fuse of 7.5 amps (upper left slot of the added
fuse block). They then ran another long, skinny wire ALL THE WAY BACK to the trailer lights connector and the taillights, and then more long, skinny wires forward to the marker lights. Do we have enough long, skinny wires running the length of the rig yet? And of course powering a bunch of non-LED bulbs (Chinook marker and taillights) PLUS whatever lights one's trailer may have.
The reason I had never blown the
fuse before is that my usual trailer has all LED lights. My solution that night was to remove about 75% of the lights on the cargo trailer, leaving the tail/brake lights, and the rear marker lights. My friend was behind me anyway, so I figured I could limp to the next rest area (this one was full and we were perched in a non-parking area close to traffic). I then made the rest of the trip in the daylight, and then ordered all LED lights for the trailer. With those, the Chinook
fuse didn't blow.
So, my question to you is, have you added ANY lights via using your trailer hitch/wiring? Are they non-LED? (non-LED draw much more is why they are a problem). If so, that's where my suspicion would lie first.
Just raising the
fuse size may be a risky proposition as there is a lot of (did I mention) LONG SKINNY wire on that circuit. And some of it is bundled (reduces ampacity). Every wire size has its rated ampacity, and that tells you how high you can
fuse it. I don't know the size of all of the wires in that circuit, so I didn't want to just put in a larger
fuse. There is a lot of wire (to potentially cause a problem). So, as I wrote above, my solution was to be sure any trailers I tow have low demands (LED lights). IF I were going to upgrade it, I'd probably re-wire so as to NOT have that super long wire going back/forward/back/forward, etc. (to the tune of 20+ feet each way). (Rather if it needed to be re-fused that could happen aft. Maybe slightly less "satisfying" to not have it all at the
fuse block, but electrical function has to be considered as well. There are other electrical choices too, but I've probably gone on long enough for now.
So summary is that unless Chinook made some big changes, your Ford taillights, Chinook marker lights, and the lights on anything you are towing are all powered by the wiring pigtail Ford intended to power just the trailer lights. And it runs back and forth and back and forth under the rig (near driver's side frame rail, and through the driver's footwell cover). So it's pretty maxed out. Adding too much draw on the trailer wiring (lights) can blow fuses.
Other ways to work with it are using LED trailer lights (not a bad thing anyway), and/or changing Chinook marker lights to LED. I imagine one could change taillight bulbs too, but I haven't looked into it. I do know you have to make sure to keep the reflector property of the stock taillights (friend who converter other brand RV to LED taillights had to add three passive reflectors to rear of rig).
If you've added anything to your rig in the way of trailer connector powered objects, that's what I'd suspect first.
Here are some supporting documents:
Excerpt From Ford's extra wiring document, showing the cutaway and stripped chassis wiring "schnozzles." Chinook used the brown one to (also) power its Ford taillights and body marker lights via the
fuse shown in next attachments.
Drawing from 2000 Chinook manual depicting their added
fuse block by driver's left shin. This drawing is for the Concourse. Premier has only one row but marker lights
fuse is also the top one, also 7.5 amps (according to adjacent drawing in manual).
Photo of actual
fuse block in 1999 Concourse. "Missing"
fuse previously powered the black/grey tank "auto drains" (shudder!).