towing lights 24v to 12v

[mc5a Jon]

I want to build a conversion box to enable my bus to plug into a standard trailer with 12 volt lights. The trailer has 2 1157 bulbs and a 4 prong plug. Turn signals flash the brake light on and off on the selected side. Running lights are the other curcuit. The bus has 6 separate 24v light bulbs: 2 running, 2 brake, and a left and right turn signal. I want to build this right and cheap. I get stumped trying to get the turn signal to flash the brake light on the trailer. I'm sure one of you has already figured this out! Thanks for any help.
Jon

[Busted Knuckle]

Craig has designed and build them! Or he will show you how!
http://bus.gumpydog.com
  BK 

[JackConrad]

Here is the way we did ours.  The relays are the little "cube" relays with 24 volt DC coils.  Jack

[bevans6]

I bought mine from Craig, he did a very nice job and added a tag for brake activation for me.  I don't consider it cheap, but less than doing it myself and top notch quality.

Brian

[Busted Knuckle]

I bought mine from Craig, he did a very nice job and added a tag for brake activation for me.  I don't consider it cheap, but less than doing it myself and top notch quality.

Brian

I didn't say he was cheap, just good!
But the only thing I HAVE found to be cheap in the bus world is ME!
  BK 

[mc5a Jon]

Thanks Jack that was EXACTLY what I was needing. I to am the the cheapest thing involved with my bus, BK!
Jon

[Chopper Scott]

I bought one of those turn/stop light converters. Now I see how Jack did it! DUH!! I should pay better attention.

[Sam 4106]

Hi Jack,
When the brake lights and either one of the turn signals are on at the same time, does the turn signal flash twice as fast as when you have one of the turn signals on alone? It seems to me that that is the way it would work since the turn signal relay would be switching from brake light on to turn signal on with every click of the flasher. That may not be a problem. Just curious.
Thanks, Sam MC8

[Sam 4106]

Hi Jack,
SORRY, after further study of your diagram I answered my own question. It will NOT flash twice as fast. I Will try to figure things out on my own in the future.
Thanks, Sam MC8

[oldmansax]

I bought one from Craig also & it is top notch.

TOM

[gumpy]

... I Will try to figure things out on my own in the future.

Seems to me you did just that...  and in the present 

[Sam 4106]

Hi Jack or Craig,

It appears that the diagram posted is for a bus with separate stop and turn lights and a towed vehicle with combination stop/turn lights. Wouldn't a different arrangement be needed for a towed vehicle with combination stop/turn lights?

Wouldn't it be better to also have a ground wire between the bus and towed vehicle so you wouldn't depend on the hitch for ground?

Are all cube relays configured the same? It would be nice if the terminals in the drawing were numbered so novices, like me, would know how to attach the wires correctly.

Our bus has separate turn and stop lights and our car has combination stop/turn lights. There is a relay system in our bus now but the turn signals don't work on the car. The tail and stop lights do. I think the PO had the relays set up for a car or trailer with separate stop and turn lights. There are five wires used on the receptacle on the bus and only four wires used on the plug of our car. I thought I would need a converter between the bus and the car but now I think if I change the wiring to match the posted drawing the turn signals will work. If my thoughts are wrong please correct me.

Thanks, Sam MC8

[daveola]

If you feel like building something, I've assembled a whole slew of options for converting 24V to 12V on my site:

  http://bus.getdave.com/Docs/12Von24V/

[JackConrad]

Hi Jack or Craig,

It appears that the diagram posted is for a bus with separate stop and turn lights and a towed vehicle with combination stop/turn lights. Wouldn't a different arrangement be needed for a towed vehicle with combination stop/turn lights? Yes, one relay for the tail lights and one for each turn signal (these take care of the brakes lights also)

Wouldn't it be better to also have a ground wire between the bus and towed vehicle so you wouldn't depend on the hitch for ground?I have that separate ground wire, just did not show it on the relay schematic

Are all cube relays configured the same? It would be nice if the terminals in the drawing were numbered so novices, like me, would know how to attach the wires correctly.As far as I know thay are all the same, but I am not sure of the numbers without looking at a relay. I think 30 is power coming in to be switched, 85 & 86 are for the coild and 87 is NO (switched power out). If it has 5 terminals 87a is NC and opens when energized. The relays I used were 5 terminal

Our bus has separate turn and stop lights and our car has combination stop/turn lights. There is a relay system in our bus now but the turn signals don't work on the car. The tail and stop lights do. I think the PO had the relays set up for a car or trailer with separate stop and turn lights. There are five wires used on the receptacle on the bus and only four wires used on the plug of our car. I thought I would need a converter between the bus and the car but now I think if I change the wiring to match the posted drawing the turn signals will work. If my thoughts are wrong please correct me.  I am not sure without knowing how the wires are conected  Jack
Thanks, Sam MC8

[gumpy]

It appears that the diagram posted is for a bus with separate stop and turn lights and a towed vehicle with combination stop/turn lights. Wouldn't a different arrangement be needed for a towed vehicle with combination stop/turn lights?

Typically, even if a vehicle has separate stop and turn lights, which most new vehicles do, we only use the the stop light for both stop and turn. It doesn't matter if you blink a separate yellow light for turn or blink the red stop light for turn. Jack's schematic will provide the blinking stop light for turn signal. My schematic actually has the ability to drive a turn signal which is separate, though I know of nobody, including me, that has done that. Most trailers you buy will have a combined stop/turn signal, so if you want to be able to pull things other than just your toad, you want to wire the toad for the most general purpose, which is combined stop/turn.

Wouldn't it be better to also have a ground wire between the bus and towed vehicle so you wouldn't depend on the hitch for ground?

Absolutely. You should always run a ground wire through your plug and harness.  It's just not shown on the diagrams.

Are all cube relays configured the same? It would be nice if the terminals in the drawing were numbered so novices, like me, would know how to attach the wires correctly.

See Jack's comments above. I agree with what he said. I think the cube relays are standard, but not 100% sure. Usually, they have a diagram molded on the relay which shows
the terminal numbers and how they work.

Our bus has separate turn and stop lights and our car has combination stop/turn lights. There is a relay system in our bus now but the turn signals don't work on the car. The tail and stop lights do. I think the PO had the relays set up for a car or trailer with separate stop and turn lights. There are five wires used on the receptacle on the bus and only four wires used on the plug of our car. I thought I would need a converter between the bus and the car but now I think if I change the wiring to match the posted drawing the turn signals will work. If my thoughts are wrong please correct me.

I expect if the PO already had relays in there, you probably just need to modify the wiring on it to match what Jack's shows, and you'll be good. You may also have to rewire the hitch plug, too.
If we get together this spring, I would be happy to help you get this fixed.


craig