An Inexpensive LED add-on for our Fluorescent lights 1

Once we got on the road and have spent more time dry camping ( no hookups ), we’ve become more energy conscious. Yes, we have solar power, but if you don’t use the power at night, you don’t have to put it back the next day. And while its not generally the biggest consumer of electrical power in our RV ( I’m going to have to give that honor to the microwave…), interior lighting adds up when you have a bunch of them on.

Our RV is a 2003 model, from an era when white LED’s had been invented, but had not trickled down to RV lighting in general, so our RV had what was the next best thing at the time: Fluorescent lights. These are nice, and from an efficiency standpoint, aren’t that far off LED’s at the light levels we as humans like to use. However, the light they provide is kind of cold and often much more than we need if we’re not reading. If we’re just relaxing in the RV in the evening or doodling with some backlit electronic device, we’d be fine with less light, particularly if it means less power consumption.


Our fluorescent light fixtures before.

Some basics on lighting geekery, specifically color, intensity and efficiency.

Light Color: I won’t go into the why, but light color is measured in degrees Kelvin. Warmer ( more yellow ) light is a lower number ( 2500-3500K ), while whiter lighting moves to the higher end of the scale, (4000-5500K). Light sources above 5500K start to look blue. The bulbs in our Fluorescent lights were 4100K and while they’re nice to read or work by, they’re a little too white/blue for relaxation.

Light Intensity: Because our eyes auto-adjust to the amount of incoming light, it’s difficult for humans to accurately judge relative brightness with any real accuracy. So, we use tools and measure total light output of a light source in Lumens. It’s not perfect, since different light sources emit light differently, but it’s what we’ve got.

Energy Efficiency: The power used by an electrical device is measured in watts, so measuring the efficiency of a light source is basically this: How many Lumens do you get out for each watt you put in? At this point in lighting development, old style incandescent ( hot wire ) bulbs are about a quarter as efficient as Fluorescent bulbs, and the LED’s in common use are somewhat more efficient than Fluorescent bulbs, though they have some other advantages ( Mostly, they’re potentially dimmable, don’t require a fragile glass tube and don’t have any mercury in them ). Fluorescents have been around for a long time and seem to be about at their efficiency limits, while LED’s are still developing fast and efficiency improves every year, even if the consumer level lighting we get is usually a generation or two behind. Still, the efficiency gap between fluorescent bulbs and LED’s can be significant and will likely continue to grow as better LED’s come out.

LED conversions can be expensive, more expensive than a $6 LED light bulb in your house. Replacing the fluorescent tubes in our lights with LED tubes ( keeping the old fixtures ) would require some minor rewiring and could cost as much as replacing the whole fixture with new LED based ones, though there are cheaper places to buy them. $32 or more, if I chose one of those options.

So, I was looking for an option that would let me add warmer LED lighting to the fixtures and keep the old fluorescent bulbs for when I needed more light, but was cheap enough that I could easily afford to do all 6 of the lights in the RV.

I considered using flexible strip lighting, which you can find relatively cheaply on eBay, but I’ve used those strips in the past and have found the quality on the cheap stuff to be pretty variable, with some of the segments failing very early. Also, Voltage in an RV can vary quite a bit, dropping as low as 10.5 volts when the inverter is drawing a lot of power running the microwave, or going as high as 15V while charging. I’m concerned that low voltage will mean dim output from the LED’s, while high voltage could significantly shorten their lifespan. So, ideally, I was looking for an LED with some sort of built in regulation.



At Home Depot one day, I found these in the discount rack for about $2.80 each:

Phillips LEDIMG_20150505_220348IMG_20150505_220406


They’re a drop-in replacement for a 12V AC halogen light bulb that looks like this:

T3 Halogen

The RV had come with these halogen lights over the dashboard which got very hot and use a lot of energy. Not long after we got the RV, I had replaced them with the above LED modules ( though they were $10 each when I bought them…). It was a nice, easy plug-and-play change ( just swap out the bulbs ) and we’ve been very happy with the LED’s, though since they’re over the dashboard, we don’t use them very much.

It seemed like too good an opportunity to pass up, so I bought the 8 LED modules that they had on hand, figuring that I could do add them to the fluorescent lights in some way and still have a few left over for spares if one burns out.  Unfortunately, Home Depot won’t be carrying them any more, but you might find the same deal I did at your local Home Depot ( Here’s a link to the HD part ), or you can get them on Amazon for about $7, or eBay.  There are about $4 worth of other parts needed to add one of these to a fluorescent light, so it’s still an inexpensive project even if you pay $7 for the LED modules.

After a little playing around, here’s what I came up with – A second switch on the other side of the fixture that runs the LED module added to the inside. Turn on the original switch and the fluorescent light works normally. Turn on the new switch and the LED light turns on. The fluorescent draws about 16 watts and puts out 600-800 lumens of 4100K light, depending on the age of the tubes inside. The LED uses 3 watts and puts out about 170 lumens of 2700K light. Subjectively, this seems almost as bright as the fluorescent. If you need more light, you can even run both.


Fixture with LED module inside

What you’ll need:

You’ll need some basic hand tools, as well as some electrical specific items:


Installation tools


Soldering Iron ( I use a portable butane one, but any low wattage iron should work ) and safety glasses. Solder in the eye is not good.


Wire cutters/strippers

Wire crimper


A drill and a drill bit the right size to make a mounting hole for the SPST switch described below. Mine needed a 7/64″ bit, I believe.

I also used a handy-dandy little device with a couple of alligator clips and a magnifying glass called a “helping hand” to hold stuff while I solder it. Amazon, if you want one.

Helping Hand

In addition to the tools ( and an LED module ), you’ll need a few more items for each fixture you convert.

A switch to control the LED  – I used an SPST mini switch from Radio Shack ( part # 275-634 ), though any mini singe pole switch will work. The rating isn’t very important, it’s not going to be carrying much power in this case ( just 3W…), but where we’re going to mount on the end of the fluorescent fixture doesn’t leave a lot of space, so a small switch is pretty important.

SPST Switch

Some light gauge wire, preferably stranded. I used 18 gauge hookup wire from Radio Shack, but I can’t find a link. I used black and red wire for this, but you do not need more than one color. The LED module is meant for 12V AC rather than DC, so it’s not polarity sensitive. How much wire you’ll need for each fixture depends to some extent on the length of the fixture. Mine are about a foot long, so I used about 3 feet of wire.

Two crimp cap wire connectors ( you could also solder the wires and tape them ). Radio Shack or cheaper at any auto parts store.

End crimp cap


One crimp-on Piggyback connector in the right size for your hookup wire. Radio Shack or cheaper at any auto parts store.


crimp piggyback

Crimp-on Piggyback connector

Some heat shrink tubing ( plus a lighter or something to shrink it…) or electrical tape.

Some double sided sticky tape, you’ll only need an inch or so.

The Procedure 

NOTE: 12V electrics are pretty safe, but the voltages that run a fluorescent light are less so. If they’re unplugged, the’re safe, but don’t mess around with this stuff while it’s potentially live. Also tools can be dangerous, blah, blah, blah. Wear your safety glasses.

Some of the images are pretty small to keep the size of this document manageable. You can click on them to view them full-size.  I’ve only done a conversion to my specific brand of fluorescent light. Yours may be different, but I think the process here will work with most any 12V fixture, as long as there’s space for the new components.  Your mileage may vary.

Find a good spot to work and set up your tools. We’ll start by prepping the LED and the switch.

Take your hookup wire and cut two pieces of wire just a little longer than your light fixture, and two pieces a little longer than half the length of the light fixture. Strip the ends and solder on of each length to the switch and the same to the LED module. Insulate the wires on the LED module with heat shrink tubing or electrical tape. Note: I used different colored wire for my installation, but the LED and the switch wiring are NOT polarity sensitive, so one color of wire will work fine, you can’t really connect them backwards.


Wire soldered to the switch.

Soldering to the LED.

Soldering to the LED.

LED all done.

LED all done.

Set the LED and switch aside for now.

Remove the cover from the fixture and take the fixture down off the ceiling.


The light, off the ceiling and on the “workbench”.

Take the bulbs out of the fixture ( they remove after turning them a quarter turn in either direction ) and set them somewhere safe, since they’re fragile.  The center part of the fixture covers the circuit board that’s needed to step up the voltage to run the fluorescent tubes. This cover is ( at least in the case of my lights…) held on with some metal tabs. Squeeze the long sides of the cover to remove it, revealing the wiring underneath. My cover was just bent metal, watch for sharp edges.


Under the cover.

On the other end of the fixture from the fluorescent power switch, drill a hole for the SPST switch for the LED. Drill it somewhat off center to allow for the wiring cover to be put back on easily.

The end of the fixture to add the switch.

The end of the fixture to add the switch.

Use the pliers to tighten the nut to hold the switch in place. On my switch, there was a little tab on the backing washer that I flattened out to make it all fit better.

My installed switch.

My installed switch.

On my lights, the power comes in next to the original on/off switch, with black and white wires. In my case, the black wire runs though the switch and the white wire runs to the circuit board that was under the cover. Find where one of the power wires goes to the switch.

Find the wire.

Find the wire.


Power Wire ID

That one!

Unplug the incoming power wire.

Take the long wire from the LED switch, trim it a little if needed ( it should just reach the fluorescent switch), then strip the end and crimp the piggyback on the end of it.

Trim the long wire from the LED switch to just reach the fluorescent switch.

Trim the long wire from the LED switch to just reach the fluorescent switch.


Crimp the piggyback onto the long wire from the switch.

Crimp the piggyback onto the long wire from the switch.

Plug the incoming power wire onto the male connector on the piggyback and plug the piggyback onto the switch where the power wire used to be.


Piggyback plugged in, tapping into power from the switch.

Jumper Connected

Detail of the piggyback tapping power from the switch.

Next, find the other power wire coming into the light. Cut it close to the circuit board, but leave yourself enough wire coming from the circuit board to strip the ends of it. Don’t cut it too close.

Cut the wire close to the circuit board.

Cut the other power wire close to the circuit board.

Strip both ends of the cut power wire. Take the long wire that’s connected to the LED and strip the end of that. Using a crimp cap, twist all three stripped ends together and crimp.

Long wire from the LED crimped to the power wire.

Long wire from the LED crimped to the other power wire.

Take the short wire from the LED toggle switch and the short wire from the LED. Strip the ends and connect them with a crimp cap. Sorry, no photo.

To recap: Long wire from switch to the power wire on the fluorescent switch. Long wire on the LED to the other power wire. Short wires from both the LED and the switch connected to each other.

Get it all back together. Put the circuit board cover back on to the fixture, tucking the wires underneath. Let the wires to the LED switch come out one side and let the wires to the LED come out the other side.

Replace the circuit board cover.

Replace the circuit board cover.

Attach the LED to the circuit board cover with double sided sticky tape. Replace the fluorescent bulbs and re-install the fixture into the ceiling.

You’re done!

The fluorescent fixture still works like it used to, but now it’s got a more efficient, warmer LED option available by using the newly installed switch on the other end.

The finished fixture installed.

The finished fixture installed.

Fluorescent only.

Fluorescent only.

Fluorescent and LED for LOTS of light.

Fluorescent and LED for LOTS of light.

LED only, providing lots of usable light and only drawing 3W, compared to 16W for the fluorescent.

Cover back on, LED only, providing lots of usable light and only drawing 3W, compared to 16W for the fluorescent.

Since we’ve installed these, we found ourselves really liking the warm color of the LED lights and use them almost exclusively. Thanks in large part to Home Depot deeply discounting the LED modules, the total cost to modify all 6 lights in our RV was under $40.

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