24 volt trailer wiring to 12v Using Relays Diagram

[frodobaggins]

Some people wanted a visual aid on how to convert 24v wiring to 12v for pulling civi trailers. Here is the way I do it using relays. Any questions or suggestions or how to improve the diagram let me know.

 

[frodobaggins]

I made it bigger. Forum shrunk first one for some reason.

 

[littlebob]

That's what I was thinking. Where do you get your 24v relays?

 

[sterlun]

Frodo this is great. I've looked at lots of diagrams but yours is really "stupid people friendly". However that doesn't stop some of us from having questions.

Am I to understand I need a 12V source to "switch" the 24V relays so that it converts my lights back to 12V? Having 12V seems to be my original problem. Please enlighten me. I have all the stuff I'm just confused on how to wire the relays. If I pull the switch off one battery isn't that a no-no because of battery balance issues?

 

[rcflyer70]

I used the same setup...works great.

 

[frodobaggins]

Frodo this is great. I've looked at lots of diagrams but yours is really "stupid people friendly". However that doesn't stop some of us from having questions.

Am I to understand I need a 12V source to "switch" the 24V relays so that it converts my lights back to 12V? Having 12V seems to be my original problem. Please enlighten me. I have all the stuff I'm just confused on how to wire the relays. If I pull the switch off one battery isn't that a no-no because of battery balance issues?

I pull off the back battery, sometimes I use a lawnmower battery. I don't believe the tail lights have enough draw to cause any serious battery balance issues as long as they are healthy.

When you pull off the back battery, 12v and 24v ground is the same, and the middle of the batteries is 12v positive. When I use the lawnmower battery I just run the 12v G and the 12v + straight to the battery.

 

[sterlun]

Ok don't laugh but, which one is the BACK battery?

 

[frodobaggins]

Ok don't laugh but, which one is the BACK battery?

The one that the negative (ground) is hooked to on the truck.
Most of the time closer to the rear of the truck in the battery compartment.

 

[patracy]

I've got a 24vdc relay board (4 relays) on the way that I plan on using to make a plug and play adapter from a spare cable off a trailer. Probably going to mount it inside an ammo box and mount the 7 plug adapter (and a 4 plug) to the side of it. Should be long enough to get it to the tongue of the trailer to strap it down there.

 

[patracy]

And those relay boards are only $18 shipped.

 

[frodobaggins]

And those relay boards are only $18 shipped.

Link please

 

[swampzr2]

PATRACY please post the link and pictures of your set-up if you have it complete. Thanks

And those relay boards are only $18 shipped.

 

[jimk]

Here is what I had drawn up for someone. Not as pretty. There is a 24relay for the e-brake control and lights (my trailer has separate turn signal and brake lights). I used a 25' 12 gauge extension cord from Home Depot for the 12v harness to the back. The auxiliary socket is to left of the licence plate. The relays are epoxied to a bit of Alum angle.

 

[quickfarms]

great

 

[skinnyR1]

Here is what I had drawn up for someone. Not as pretty. There is a 24relay for the e-brake control and lights (my trailer has separate turn signal and brake lights). I used a 25' 12 gauge extension cord from Home Depot for the 12v harness to the back. The auxiliary socket is to left of the licence plate. The relays are epoxied to a bit of Alum angle.

Ok. I am duplicating this, and I have everything I need to do so. The question I have involves the wiring of the brake signal and turn signal.

If it is wired per the diagram, won't the turn signal not flash when the brake is depressed? The brake and the turn signal share the same light, I believe. Since the circuit will be closed by depressing the brake and closing the brake signal, won't this cause the corresponding light to be on, not allowing the light to flash?

Am I reading this correctly?

 

[Sephirothq]

look at how your lights work right now when the turn signal and the brakes on.

 

[skinnyR1]

Is there no turn signal when the brakes are on? I am not near my truck at the moment.

 

[Wildchild467]

That diagram is exactly how I planned on wiring my trailer lights up someday. I have a seperate alternator for my 12 system, so getting 12 volts is not a problem at all. Nice to see a diagram!

 

[jimk]

I made that for my 1993 Talbert Equipment trailer. It has 2 bulbs on each side of tail, a Trucklite brake light (twin filament uses one) and a turn signal/ tail light (twin filament uses both), if I recall correctly. My 97 Ford Ranger has a factory module under back bumper between harness and trailer wire connector. It changes the trucks amber turn signals and red brake lights to a single signal for the trailer. That trailer, a hacked 105, uses a single generic twin filament bulb (on each side). Module is a common aftermarket part at trailer supply stores. Mine failed a few years back making for some strange behavior. I either got a used factory part at pick and pull or a new one at NAPA. I recall spending about 40$ so probably the latter.

 

[jimk]

Photo above

My diagram above really sucks. Here is a photo w/ added clarification.

Only 4 wires (from the army trailer cord) shown w/o cover, inside the box, at extreme left corner (tied together w/ zip tie) are being used. The photo does not show that some are not connected