Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 14, 2025 ...

Hi all,

I'm trying to add a PWM dimmer (like the ones below) to the vanity lights in the bedroom.  It seemed like it would be easy enough.  I wired it up temporarily to test it out and weird things started happening. 

Motor Speed Controller PWM DC 3V 6V 12V 24V 35V 5A Speed Control Ultra Small LED Dimmer

Dafurui 2Pack Upgraded 6V-90V 15A DC Motor Pump PWM Speed Controller 16KHZ Regulator Module Board

After a bit of probing with my multimeter, I think I finally figured out the issue.  The way these dimmers work, the entire circuit needs to happen downstream of the switch.  What I mean by that is, the circuit needs to be laid out as follows:

12V power into the dimmer -> to the + lead of the light -> to the - lead on the back of light -> to the - on the load side of the dimmer -> then out of the dimmer to ground.  If the circuit is wired this way, all is well.

If the circuit does not ground through the dimmer, it does not work correctly. 

12V power into the dimmer -> to the + lead of the light -> to the - lead on the back of light -> to the motorhome's common ground.  This circuit would not work correctly.

So what through me for a loop was that each side of the vanity lights were behaving differently.  One seemed to be working properly, and worked exactly as it should, when wired alone.  When I added the other light, things went sideways.  Finally, I realized the second light is screwed to the outside wall, and I'm fairly certain that the mounting bracket is screwed into the metal frame of the coach, which is becoming the ground and completing the circuit; not traveling back through the dimmer, but around it. 

So, how do I overcome this rather odd issue??

It seems that even if I found a replacement fixture, if it has a metal frame and that frame is attached to the wall with metal screws, it's still going to be the shortest path to ground.

Which led me to, what if I didn't use metal screws?  What if I screwed the frame to the wall with non metal screws?  Would that work?  Would they hold the weight?  Would I burn the coach to the ground?

Delrin/nylon screws are very common in computers, and electronics.  There is a fairly large assortment available, I'm just not finding anything with coarse threads like the screw I took out of the light fixture's frame. (see pic)

M3 Nylon Pan Round Head Machine Screw

Prime-Line 9097372 Hex Head Cap Screws

I've also included a pic of the light, which lacks any sort of ground other than the frame.  Foretravel did wire both frames to ground, which is why the one light works.  But they also screwed the frame to ground which is why the other light is misbehaving.

I've included pics of what the circuit should and should not look like.

So what would you do?  Would you go with plastic screws?  Would you just tell the DW, "sorry, no can do?"  Or does anyone else have any other ideas of how to overcome this? 

Doug I don't have an answer to your question. Sorry, but I can tell you what I did. On my coach in the bathroom there are four light circuits. Two of them were overhead lights, which were fluorescent at one time. There are two under cabinet puck lights, and these were wired together with one of the overhead lights. So when you switched on the overhead lights to pucks on as well. And there was a over the mirror light that had three bulbs. Not the round kind like you have but I guess that's what they were originally maybe? A previous owner had put in LED bulbs there. I didn't like that arrangement. What I did was I separated the puck lights from the overhead light. I did this by severing the wires and went to the light in the light itself. I then ran a wire from the rear overhead light that's next to the bedroom to the overhead light in the bathroom. Since both of these are now LED strip lights I use 16 gauge wire which is more than enough. So now when I turn on the overhead lights both come on, if I want just a little bit of light I turn on the puck lights, and if you just want to look in the mirror then there's the over mirror light. And of course there's also the under cabinet light which I changed to LED as well. Put that switch all the way by the front door. Not sure what that was about. I meant to interrupt that circuit put a different switch in the bathroom for that light but didn't do it.
As far as dimming the overhead light, mine is on the inner bulkhead which would not be grounded to any metal frame I don't think. If your vanity is facing the outer frame then yeah I guess that could happen. A non-metal screw should take care of your grounding problems if that is indeed what the problem is. It's worth a try.

quick edit. After looking at your pictures again it looks to me like those are in the lights from the bedroom vanity? If so I got rid of those as well. Initially I made lights out of walnut stock that I had on hand with a LED strip in it, but they were too bright. I switched them out for a 12 volt RV LED light I purchased on Amazon. David gave me the idea of that light.
RecPro-Vanity-Light