12v DC modifications to my 1640LTD - Thoughts and opinions?

[Nrollins]

Hey gang, new member, first post. We just bought a 2021 Rockwood Freedom 1640LTD pop-up camper, and are immediately loving it! But I already have my sights on some electrical mods, and would love to get thoughts. Feel free to point me to other threads or off-site resources if that’s better. I know a lot about 120V AC work around the house, but I’m entirely new to 12V DC work (or even wires and fitting types!)

Basically I want to do two 12V projects around my extinguisher location, hopefully tapping into the wires coming to my overhead lights switch. The more complex project is to tap into that line and introduce a dimmer for those overhead lights. I don’t 100% know if they can be dimmed, but I can always test the controls before cutting in new holes. The 1640 uses very small form factor switches from Sigma Switches, and unfortunately they don’t make dimming switches at all but I’ve seen various slider and dial dimmers for 12V, so I’m betting this is possible.

The other project is to put in a switched combo voltage meter/cigarette lighter device (lots of devices out there like this for boats https://www.amazon.com/dp/B08CDTWT1L...ing=UTF8&psc=1) I’m assuming if it’s inline on the 12V system, it will give me a readout from the door of my battery status.

Like I said, I don’t know much about 12V DC wiring diagrams or fittings, and haven’t seen examples of people doing this work, but I’d love to hear any of your ideas. Thanks!

[chriscowles]

Whether or not you can use a dimmer depends on the type of light. I (and others) successfully added a dimmer to Mini-Lites. I used this dimmer. Note that it needs a ground, in addition to the hot line passing through it.

[Nrollins]

Originally Posted by chriscowles

Note that it needs a ground, in addition to the hot line passing through it.

Thanks Chris, that’s great feedback. That’s one of the dimmer types I’ve been looking at. Not sure there is a ground going to the current light switch...looks like just two wires going to a slip-on connector (not sure what they are called.) If that’s the case, any thoughts on how I’d find a ground to tap into?

[chriscowles]

Originally Posted by Nrollins

Thanks Chris, that’s great feedback. That’s one of the dimmer types I’ve been looking at. Not sure there is a ground going to the current light switch...looks like just two wires going to a slip-on connector (not sure what they are called.) If that’s the case, any thoughts on how I’d find a ground to tap into?

You can ground to the chassis, as long as you get a good connection to the frame. Alternatively, if the intended location for the dimmer is anywhere near the fuse panel, run a single wire to the common negative terminal there.

Edit: to clarify, it needs a negative connection. Since the common negative bus bar at the fuse panel almost certainly has a link to the chassis, that's why a chassis ground works. (Just as 12V vehicles are negative grounded to the chassis.)

[Nrollins]

Originally Posted by chriscowles

You can ground to the chassis, as long as you get a good connection to the frame. Alternatively, if the intended location for the dimmer is anywhere near the fuse panel, run a single wire to the common negative terminal there.

Edit: to clarify, it needs a negative connection. Since the common negative bus bar at the fuse panel almost certainly has a link to the chassis, that's why a chassis ground works. (Just as 12V vehicles are negative grounded to the chassis.)

Gotcha...I read a little more about 12V/vehicle wiring and am starting to understand the difference (simplicity.) The neutral/negative/etc line back to the battery IS the same as the “ground” when it comes to these systems.

Next time I pop things up, I’ll look further behind the switches and see what’s available. The furnace is directly above, and since (I believe) that gets 12V power,there should be ground/negative/return/etc there. Will it matter that they’re on different fuses, since it’s all going back to a common negative bus bar?

[pgandw]

No, any return path will work unless something weird was done (a switch put in the negative instead of the positive). If your pop-up is like either of my FR hard-side pop-ups (A-frames), there is no negative bus bar. All the negative wires were tied together in a rat's nest series of wire nuts behind the electrical panel, with one wire going to chassis ground.

When I replaced the WFCO converter, I put in a true bus bar, removed the wire nuts, and re-homed all the negative connections to the bus bar.

Just preparing you for the likely reality.

Fred W
2019 Flagstaff T21TBHW A-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time

[Nrollins]

Originally Posted by pgandw

No, any return path will work unless something weird was done (a switch put in the negative instead of the positive). If your pop-up is like either of my FR hard-side pop-ups (A-frames), there is no negative bus bar. All the negative wires were tied together in a rat's nest series of wire nuts behind the electrical panel, with one wire going to chassis ground.

When I replaced the WFCO converter, I put in a true bus bar, removed the wire nuts, and re-homed all the negative connections to the bus bar.

Just preparing you for the likely reality.

Fred W
2019 Flagstaff T21TBHW A-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time

So helpful, thanks Fred! I’m going to try the tiny dial dimmer, and see if I can core a hole to mount it directly into my Awning alight blankout (my tiny PUP doesn’t use that spot.) that way I can maintain as much of the original switching design as possible.

[Larry-NC]

Originally Posted by Nrollins

Thanks Chris, that’s great feedback. That’s one of the dimmer types I’ve been looking at. Not sure there is a ground going to the current light switch...looks like just two wires going to a slip-on connector (not sure what they are called.) If that’s the case, any thoughts on how I’d find a ground to tap into?

Some folks in the trade call them FastOn. I think that's a brand name of AMP.

[PenJoe]

By describing your location, it appears the the fire extingguisher would be on the side of the furnace. It would be logical to catch a ground at the furnace.

In household a/c wiring, there is a wire color code. When it comes to 12 volt systems, not so much. Most often, a red wire is positive. The pairing wire may be white, but it could be black. A black wire could be positive or negative, most likely positive if the pairing ground wire is white. But, on a dual battery, a white cable may connect two positive terminals wired in parallel. Green most often is a ground. The battery is grounded to the chassis as in automotive. All circuit grounds terminate to the chassis (frame). In the past, I have made a simple circuit tester from a 12v marker light and two pigtail wires.

Looking at your Amazon link, the red is positive (giveaway is the fuse) and black is ground.The red should mainline to the battery. Make certain of couple things. That device extends well past 1.5" behind the cabinet panel once the wires are attached. Make sure the wires are not affected by the furnace heat and that and that there is adequate clearance to install the device. Check for wires and pipes as-well-as the furnace. They may not be well organized. Camper space is scarce behind walls and panels-like putting 2 lbs of beans in a 1 lb bag.

[Nrollins]

Thanks everyone. Another 12VDC question...things I’ve been reading have people recommending 12ga wire. 12ga is heavy stuff that I’d use for 120V 20A in a house...is there a different type of “12 gauge” wire for 12VDC work that I don’t know about?

[PenJoe]

Originally Posted by Nrollins

Thanks everyone. Another 12VDC question...things I’ve been reading have people recommending 12ga wire. 12ga is heavy stuff that I’d use for 120V 20A in a house...is there a different type of “12 gauge” wire for 12VDC work that I don’t know about?

That would be 12 ga stranded wire as opposed to 12 ga solid.

[Larry-NC]

Originally Posted by Nrollins

Thanks everyone. Another 12VDC question...things I’ve been reading have people recommending 12ga wire. 12ga is heavy stuff that I’d use for 120V 20A in a house...is there a different type of “12 gauge” wire for 12VDC work that I don’t know about?

It's not really different wire, but it's much more common to use stranded wire than solid wire on the 12V stuff.

The same general rules apply. 14 AWG if it's fused 15 Amps, 12 AWG if it's fused 20 Amps (rare). You may run into many situations where the wire branches off and there's an inline 5 Amp fuse and the wire beyond that is 16 or 18 AWG. (Not all fuses are at the distribution board.)

[Quilter3446]

Hi Nrollins.
Sounds like you are starting off in the right direction - thinking about your modifications right off the bat.
Good input on the dimmer - especially if the lights are LEDs.


As far as adding a 12v outlet, just be cautious of the amperage requirement of whatever you are plugging in.


Years ago we did the same thing to run a small oscillating fan to our pop-up when boondocking.


Many other 12v devices out there draw a lot of current.


Be especially cautious if you are connecting to the 12v circuit in the top of the pop-up. It may be a fairly low amperage circuit.



With your knowledge of 120v circuits you have the basic concepts you will need.


Enjoy!