2020 Silverado trailer brakes not working.

[Brummie99]

Took the first major trip of the season yesterday (about 300 miles) towing a 5th wheel.

 

Trip was uneventful until about 5 miles from destination when I had to take a sharp (about 120 degrees) right turn. As I made the turn, I heard a pop from the rear of the truck and immediately got the message to check trailer connections. I pulled over and checked. removed and reseated trailer connector and could smell an electrical burning smell.

As we were only 5 miles to go, I proceeded anyway (dumb, I know). When we arrived, the connection box in the kingpin was warm to the touch and can still smell burning.

I removed the cover from the kingpin connection box and the wires were still hot but don't see anything visibly burned.

This morning, I'm trying to troubleshoot. When the trailer is connected, the trailer app shows it connected and all connections are OK. Lighting test works.

The only problem now is no trailer brakes. The truck doesn't recognize there is a trailer with brakes attached. No light on the trailer slider/switch. Although when the trailer is connected, I get the message "trailer brake gain restored".

The 30A fuse #84 for the trailer brake is good.

I suspect the "pop" may have been the trailer breakaway connector getting pulled out. Not sure but it was disconnected when we got to site.

 

Below is a picture of the wiring box on the 5th wheel. No sign of burning. Any idea what the device is at the top-left with 2 studs? It has 12V on both sides with or without the truck connected.

 

Any ideas where to go next?

 

TIA

 

[Brummie99]

To add to the above...

Ran the trailer diags in the trailer app and that shows a problem with the electric brakes.

 

[Steve-2019]

I'd be checking out that trailer breakaway switch (internally).

[brianf60]

That is a circuit breaker. 

[brianf60]

The heat points to excess current. Usually this cause by a circuit shorting to ground. The first step in diagnosing this is a visual inspection. Follow the wires from there all the way to each brake assembly. Most likely a wire has rubbed against the frame. Often you will also see signs of corrosion on the wire. At least in rust belt. 
 

Blue wire is generally used for electric brake circuits. Hope this helps.

[Brummie99]

Thanks for the responses. I haven't had a chance to look any closer. Will be checking again tomorrow.

The trailer is 4 years old but has been towed less than 1,000 miles in that time (including 300 yesterday). We're based in Florida, so not a major rust area.

I will probably replace the breakaway switch anyway but still curious about the black device.

 

 

[Brummie99]

I have a short on the brake circuit on the trailer. Possibly a bad magnet.

I have a mobile RV tech coming on Friday.

 

[Brummie99]

*** Update ***

The mobile tech was a no-show, so I checked it out myself and found 1 wheel shorted. The others tested seemed OK on the multimeter.

Ordered 2 replacement magnets (so i'd have a spare).

Tried installing it this morning but when I removed the hub, the remnants of the brake material fell out and the wires leading to the magnet were completely fried.. Didn't bother checking the others.

So, now I have 4 complete new brake assemblies coming tomorrow.

 

[Brummie99]

Replaced all 4 brake assemblies.

The first one was completely trashed with burned wires and zero brake lining. Second one the magnet was partially melted.

The other 2 looked OK but replaced them anyway.

Also replaced the breakaway switch.

Drove 60 miles to our next campground with no issues.