Revisit Toad Stop/Turn/Tail Lighting

[Scott & Heather]

I dug up some dusty threads from 2006/2007...but nothing really answered my questions...really just made my allergies worse more than anything. Our coach isn't wired with a trailer lighting harness, so we're starting from scratch. Can someone possibly explain in baby terms (this should be in the tech archives) the process by which I can wire up some toad lights? I know there are multiple ways to skin this cat, but in the interest of time, a quick/easy/simple (kiss) system that can get us on the road in a week would be helpful. I've seen that some of you use magnetic lights, which is great, but how are you converting from 24 to 12 volt? I can't get an auto parts store around here to find 24 volt bulbs in stock. Diodes, relays, etc is a project for this winter when we're in Florida. Until then, I need simple and quick. Thanks so much for any and all help.

Scott

[bevans6]

I use a relay based converter.  it takes the 24v signals to the tail/turn/stop lights, combines them and converts to 12 volt.  I bought one from Craig Shepard, not sure if he is still willing to make one.  His uses the same relays as the MCI does, so common spares, etc.  He modified his standard design to give me a 12v feed to the brake converter - normally brake and turn signal is combined at the 12v stage.  His page on it is here, and is part of possibly the most excellent site on converting a bus that there is on the 'net, as far as I'm concerned.

http://www.gumpydog.com/Bus/MC9_WIP/Electrical/Tail_Light_Converter/tail_light_converter.htm

Brian

[Lin]

The Gumpy method is first class, but I am not and therefore use magnetic lights.  I just changed the 12v bulbs in the lights to 24v bulbs.

[Scott & Heather]

The Gumpy method is first class, but I am not and therefore use magnetic lights.  I just changed the 12v bulbs in the lights to 24v bulbs.

And where on earth did you get the 24 volt bulbs? Also, how did you wire the magnetic lights to your coach? Did you splice into the wires going into the actual coach lights?

The Gumpy method is something I plan to do in Florida. Until then, unfortunately we are short on time. Ordering relays, having them shipped, and having to swim my way through the electrical maze of our coach is tough at this point. We've been hammered the last few weeks.

[thomasinnv]

you can get add on lights from camping world for around $20 that you drill a hole in the rear light housing and add them in on the toad. Then you can run 24volt lights if you want, or install a relay converter system. I made my own relay setup with 4 standard automotive relays in a water tight box so I can tow anything without having to worry about compatibility.

[Lin]

24v bulbs are available online or from Napa.  Remember though, sometimes Napa calls them 28v bulbs.  I have wired the receptacle by just splicing into the appropriate directional, brake, and tail light wires.  If the brake light is completely independent of the others, I believe there is an adapter that will combined them for your magnetic lights.  I don't know if the 12v one will work for 24v though.  When I did mine, I was also moving and had to get it done fast so I mounted an extra light on top of the magnetic fixtures and ran the brake light directly to that.  I thought I would do something better down the line, but I'm still using it the way it is.  Lazy!

[Bill B /bus]

I have found that the best/easiest/simple way is the relay route.  You can buy 24VDC relays. As written above NAPA calls them 28V.  I use five relays. In no particular order: stop, tail, left, right and backup lights. If an MCI then pull your relay coil power from the engine control panel. The 24V power goes to the relay coil. Feed 12V to the input terminal, memory serves is labeled 30. The out going 12V comes from the 87 terminal. Feed these 4 or 5 wires to your male trailer connection of your choice. I use a 7 pin round. Some prefer the 7 flat, a bigger pin and plug. Then feed the 4 or five conductors to the rear of your vehicle. Splice into the appropriate bulb supply wire and place a diode, electrical check valve, in the normal vehicle supply wire. This prevents the buss applied electrical; current from backfeeding into the vehicle electrical system. I know it shouldn't be a problem but with today's computers why chance it. I run the wirew bundle under the car and up through the trunk or if a wagon then in through one of the side cavities behind the rear wheels. I have wired some 7 or 8 vehicles this way without problems. If you want to tow a trailer then just use a 7 round to 4 flat converter to hook to the trailer connection.

Materials: i 1 watertight electrical box (preferred), 4 or 5 relays 24V coils, 14 gauge wire different colors will make your life easier, male and female connector of your choice, mountings for said connectors, diodes (I use the 50amp/50 volt diodes from Radio Shack).
You will spend a day for the whole job.

Re: magnetic lights. I don't like them as they may or may not stay where placed. Finding a car being towed with no lights shining is not fun. The vehicle had the magnetic lights laying face down on the trunk. 

Bill

[fraser8]

I used the Grumpy Dog diagram and bought the relays and a water tight box from an industrial electrical wholesaler. It is a nice professional working and looking installation. I have two sets of wires coming out, one set uses a separate brake light/turn signal and the other goes through a conversion box (from a trailer supply) and has a combination brake light /turn signal set up. I also installed diodes in the tow vehicles to prevent back feeding. Nice and easy, just plug and go. I will thank Grumpydog for the helpful articles.

[Bill B /bus]

I would add that I changed over to 12V LED lighting for all the exterior lights. In front the clearance lights are resistor limited for current.  The front and side turn signals are still 24V bulbs. The relay system allows the easy installation of the 12V LED assemblies.

Bill

[artvonne]

  Any aviation shop at an airport will have 24 (28) volt lights. Just explain what your after and they should be able to match something. Nice thing about Aviation lights is most are rated at 10,000 hours or higher.

[Scott & Heather]

Thanks for the very detailed responses Heather is painting the dolly some new colors When she's done. I'll wire everything up. Thanks again...

[Scott & Heather]

Hi friends. I've now spent two days making phone calls, driving to various auto and truck parts stores, and have had absolutely zero luck finding 24 volt bulbs, lights, or even 24 volt relays to make Gumpy's system. Tried Radio Shack, NAPA...no luck. So, I finally found a place that has P21/5w bulbs in 24 volt which are direct replacements for the bulbs found in most trailer lighting kits (Harbor Freight, Walmart, AutoZone, etc.) Double and offset bayonets and two contacts/two filaments. I already own the lights and will buy two more cheapo sets tomorrow...mount them all in a row, and run a wiring harness to the coach at which point I'll splice into the coach tail/stop/turn lights. Other than being ghetto, I assume this will work to get me on the road Friday. Once we get to Florida, I will be changing this system to the Gumpy method. Until then, I have to get legal. Only reason we're doing this last minute is because concert dates changed last minute for me. Otherwise we'd have another couple of weeks. I hate rushing last minute. But this was inevitable. 

[Oonrahnjay]

(snip)  I hate rushing last minute. But this was inevitable. 

   Yeah, i hate that too but it sounds like you'll be OK.  Have a safe trip!

[desi arnaz]

Easiest way is to go to haul and rent the smallest trailer, they will wire you up for free if you buy the pigtail.

[rv_safetyman]

This subject comes up every once in a while and always starts out:  I am leaving tomorrow and I need a trailer connection that will convert a 5 wire system to 4 wire system and 24V to 12V    It always seems to get overlooked until the last minute.

In the March 2009 my article on the subject was published.  It contains quite a bit of detail of what is involved in doing the job correctly - at least in the opinion of Sean Welsh, Craig Shepard, Jack Conrad, and myself.  I present the best of all those folk's designs in the article.  More importantly, I list sources for the relays (including 24 volt).

For those of you who plan to tow and want to plan ahead, contact BCM and get a copy of the magazine.

Jim