24 volt to 12 volt for a reailer brake controller

[Jon Wehrenberg]

Bill,

Jim has it right and rather than add to or confuse the issue I suggest you and he communicate via some simple wiring diagrams. I think you are not yet clear on how simple this is. All you are doing is using the signal circuit (whatever you pick, such as a brake light wire) to energize a coil that closes electric contacts to close the 12V brake controller circuit. Four wires. 2 to the relay coil (one of which is a ground wire), one 12V in from your 12V power source, and one 12V out to the brake controller.

[JIM CHALOUPKA]

Bill,

Jim has it right and rather than add to or confuse the issue I suggest you and he communicate via some simple wiring diagrams. I think you are not yet clear on how simple this is. All you are doing is using the signal circuit (whatever you pick, such as a brake light wire) to energize a coil that closes electric contacts to close the 12V brake controller circuit. Four wires. 2 to the relay coil (one of which is a ground wire), one 12V in from your 12V power source, and one 12V out to the brake controller.

Jon, I was only trying to help Bill understand the principal of what he was trying to do. (with the hope he could see the light and do it on his own)

As far as specific help about his bus, well, not having one of my own, I don't think I could do that in all practicality.

[Jon Wehrenberg]

Jim,

This is a case where bus specific information is not required. What Bill needs is a wiring diagram or even a relay part number and an associated diagram to suit his needs.

Where Bill opts to pick up his 12V and his 12V or 24V signal is entirely up to him because only Bill at this point knows to what extent he wants to fish wires or where he wants to locate his controller and relay.

Bill could locate the controller in the big electric box in the rear (but lose the opportunity to be able to adjust it as needed) or he could opt to locate it at the driver's area. Likelwise the relay can be located where convenient for his purposes. He can get signal power from the brake light switch if he wants to get it from the front, or he can pick it up from the rear from such sources as a brake light wire or even from the signal circuit from the brake light relay.

Where and how is unimportant. The only thing Bill needs now is a wiring diagram and maybe a part number for a relay.

[billbunch47]

I think a light bulb just went off. It seems to be going backwards but there is a spare wire close by , I was thinking at the source but somewhere in the system it has already been done for me because the brake light signal out to the trailer or toad is already 12 volts might as well try to use it. Will let you know, Thanks John & Jim, Bill

[ajducote]

There are a bunch of examples on the internet on wiring relays.
here are a few to look at.

http://www.the12volt.com/relays/relays.asp

www.installdr.com/TechDocs/999404.pdf

Andre Ducote
1999 Royale

[Jon Wehrenberg]

Bill,

That is why I mentioned the trailer receptacle earlier. On both my Prevost coaches the toad plug wiring had relays for each circuit (brake, park, turn signals) and the bus lights powered the relays which switched power from the 12 volt post.

You are correct in that it can likely handle the load. You may wish to follow your circuits however to make sure everything in there is sized to handle the extra load. You could have insufficient wire size, a circuit breaker or relay of inadequate size or you could have relays limited to the amperage you pull for the lights. You would not want to need a fast stop and then find the trailer brakes won't work because you tripped a breaker, or worse started cooking some wires. I can speak authoritatively about how ugly it gets when your Prevost is burning.