Damaged hitch relay board

[amt]

I discovered my hitch relay board has some kind of failure. I have what appears to be a burned out connection where a relay plugs in. This relay is for one of the two trailer connectors (the 7-wire).

Any idea why this would happen? Wouldn't a fuse or circuit breaker trip before something like this happens?

Do you think this board is repairable?

Should I bother repairing if the 6-wire trailer connector still works? 6-wire connector has turn and brake lights combined, where as the 7-wire has separated turn/brake. The burnt relay connection is for the 7-wire connector only.

Would I be better off just building something new starting with this: https://www.waytekwire.com/item/4635...2-0-1-0A-RFRM/

[Hoffman]

Wow that board looks like it was cooked good. I would guess that this is fixable, the components seem commonplace, however I can't read the schematic, too fuzzy, so not sure what cooked. However this is not a job for someone who's not done circuit boards previously. And likely will require some jumper wires to bypass the printed board paths that may have burned. Fixable? Likely. And with the schematics, should be an easy task for the appropriately skilled.

As to why it happened, the external circuit breaker trips only when excessive power is drawn. But in this case the component looks like a relay which basically bridges between lower amperage control wiring and higher amperage functional wiring. In this case, you may not have drawn excessive current, but just exceeded the capacity of the component (Relay). You're right, it shouldn't happen, but shit happens.

[amt]

I think I re-uploaded the schematic drawing in full size, but you have to click on the attachment to see it in full detail. The relay in question should be marked as "K5B" on the schematic, but marked as "K7"
on the board. It would be nice if they had those marked the same! Anyway, if I followed the traces correctly, this is for the 7-pin right turn signal.

[Joe Camper]

Unless u r pulling the titanic with a half town of lighting U don't need any of that. Trace those wire to the source in the engine room fuse panel and run a 7 wire cord down to your coupler at the bumper.

Semis pulling doubles and tripples dont even use kit like that. Simple inline circuit breakers will suffice for protection.

[Gil_J]

These converter installed trailer interfaces performed 2 functions. Most relays simply isolate the Prevost source from the dedicated power going to the board and through those relays to the trailer connector. The isolation relays are a really good idea. The other function is to combine brake and turn lights. The 3 to 2 conversion is easily done with commercially purchased devices. Yes, each trailer side functions should have been fused. Fusing isn't always done as it should be done by many converters. You could rebuild the function with relays a converter and fuses. If can be accomplished professionally without building a circuit board based solution.

[Joe Camper]

I understand it's on the bus and I want it whole, I get that loud and clear.

Not I bit of it is nessessaary. Most toad wiring comes will all the protection nesessary. Breakers, diods ect.

[amt]

Thanks for the feedback. I had no idea there were converters that did the turn+brake into one. I guess this hitch relay board is a case of Vantare being overly cautious and wanting to separate the systems as Gil stated. Too bad they did not include fuses. Anyway, after sleeping on it, I think I will just repurpose the circuit for the reverse light for that damaged right-turn light, and then use the 7-wire connector (with separate turn and brake lights) to wire up my toad. Either that, or I will wire up a new relay (not on the board) for the right turn light so I can keep the reverse light (for whenever I do have a trailer). I think I happen to have a couple spare relay + socket + wire lead lying around to do that.

Perhaps I am going overboard, but I really like the idea of having the turn signal lights and brake lights separate on the toad. The wiring is easier on the toad, and I get *all* of the brake lights lit up, including the third brake light.

Joe, you are probably right it does not matter, but I will err on the side of caution here. You never know, maybe I'll have 240 watts of trailer brake lights some day

[Gil_J]

Andrew, just know that the standard wiring for a 6 wire connector common on a towed doesn't support dedicated brake lights. But it does support an electric brake signal, that is the same function unless you are using an electric brake controller.

[Joe Camper]

To isolate the prevost source to the dedicated power going to the board.

This is a perfect example of what I believe is the acclies heal of prevo conversions.

Over engeneered to death.

[Gil_J]

Joe, on this one we'll have to agree to disagree. When Prevost didn't factory supply trailer wiring support it's a good engineering practice to isolate the Prevost source from that being supplied to the trailer. Prevost didn't engineer their lighting systems for added lighting. Even if they had, why chance having a short circuit in whatever you are towing affect the Prevost lighting? The best I can tell, all converters designed their own lighting isolation system when Prevost didn't supply trailer lighting support. None simply tapped the Prevost circuits and extended them to the trailer plug. Even my somewhat simply converted Hoffman included isolation. I'm pretty sure your American P trailer wiring is isolated from the chassis' lighting, isn't it?