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/46357/EATON-s-Bussmann-Series-15404-2-0-1-0A-RFRM/

http://forum.prevostownersgroup.com/attachment.php?attachmentid=18080&stc=1http://forum.prevostownersgroup.com/attachment.php?attachmentid=18079&stc=1http://forum.prevostownersgroup.com/attachment.php?attachmentid=18081&stc=1

[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?

[Joe Camper]

No it is protected with circuit breakers and spade fuses. I'll email u a picture of the schematics for all 379 model peterbilt that was about a 15 yr run so more than a few. Mac KW Freightliner all of them r void of this converter added board of protection we r discussing.

I quite electrcly ignorant so I'm still trying to wrap my brain around isolate power source from dedicated power.

What protection does that board and relays provide that a circuit breaker and possibly a diod would not?

Please enlighten me yoda sparky.

[Joe Camper]

18083

18084

The firewall side where it says trailer that's my 7 wire to the trailer going into that loom protector.

This is the American version of protection for comparison and discussion.

This is the front and back of peterbilt fuse panel. Only 3 relays total. They separated the headlights and relayed those and the horn. PERIOD. Even the power for the marker lights, trailer included run right through the switch on the dash. Blower motor spade fuse and through the switch on the dash. A/C clutch spade fuse and through the switch on the dash.

18085

As for towed electrical protection all trailers all have a female receptical like this one that house 7 circuit breakers.

This represents decades of production.

[amt]

Well, I have moved the right-turn light to the reverse light circuit (removed the reverse signal), and I removed the electric-brake signal from my 6-wire connector, so I could have: ground, battery-charge, left-turn, right-turn, stop, & driving (tail) lights. I realize this is not standard wiring for a 6-wire connector. I have not yet tested with everything all connected, but I did test with a voltmeter at the end of the coach, and oddly enough, when one turn signal is going, I get a faint signal on the opposite turn signal, like 2-3 volts on and off. I suspect this is due to that overly-complicated mess of relays that have to combine the stop and turn signals. So I may just remove those particular relays, as I am not using the combined turn and stop right now. I plan on leaving on the 26th for a short trip, but we may just choose to not pull the toad this time.

Eventually, I will redo all of this, and I am leaning towards one of these: https://www.etrailer.com/Trailer-Wiring/EZ-Connector/319-S14-07-6.html
It's a little bit more expensive, but IMO far nicer than anything I have ever seen for trailer hook-ups. 14-wires can get me anything I could possibly need, and they provide adapters to standard trailer connections, in the rare case I would need that. 14 conductors allows me to have pretty much all combinations of signals and power, and it looks like the company will even build you a custom cable (should you need something like a lower gauge wire): https://cdn.shopify.com/s/files/1/0355/4007/4632/files/14_Pin_EZ_Connector_Spec_Descriptions_06_01_21.pdf ?v=1622573679

One other thing I plan on doing is using an actual DC battery charger for the charge wire. I do not think it's a good idea to wire the two 12v systems directly together. If one battery is low, the other may produce so much current that you are very likely to blow a fuse or trip a circuit breaker, or if you do not have those, melt a wire. I'd rather have control over the max amperage going to the toad battery. I already have the charger (Renogy, 20A, but can be set to 10A), so if I am feeling up to it, might wire that in tomorrow.

[Gil_J]

18083

18084

The firewall side where it says trailer that's my 7 wire to the trailer going into that loom protector.

This is the American version of protection for comparison and discussion.

This is the front and back of peterbilt fuse panel. Only 3 relays total. They separated the headlights and relayed those and the horn. PERIOD. Even the power for the marker lights, trailer included run right through the switch on the dash. Blower motor spade fuse and through the switch on the dash. A/C clutch spade fuse and through the switch on the dash.

18085

As for towed electrical protection all trailers all have a female receptical like this one that house 7 circuit breakers.

This represents decades of production.

Dang, 30A taillight and 35A brake lights! Oversized wire and fuses is one way to do it. That must be #8 wire.

[Gil_J]

Andrew,

The faint voltage on the turn signal is a poor ground or, as you suspect, the combining function electronics. There's no way I'd consider a non standard connector. 6 and 7 pin connectors work and if you need to replace one on the road they are easily found. If the vehicle needs seperate brake and turn lights, use a 2 to 3 converter. I've used a 3 to 2 on my coach and 2 to 3 on my Explorer for years. There's a much better choice than running a battery charger. Here's a regulated power system.
https://rvibrake.com/products/towed-battery-charger-plus

[Joe Camper]

"Oversized"????????

No those r the correct components to achieve simplicity and reliability. That's how the groceries get to the store. Void of circuit boards that create the very problems they r put in to avoid.

I do not think the loom is constructed of #8 wire Gill I will have to check.

The dash power is fed through an 80 amp relay not on that panel rather up behind the dash but that's it.