Electrical Power Inlet: Look Out!

[SteveandTerri]

The wife and I have been on the road in Sisters, Oregon for the last 10 days. A few days ago - all of a sudden - the TV, Microwave Oven, and Fireplace stopped working. This was the second time this had happened. The first time everything came back ON after about 20 minutes. This time the appliances didn't come back ON.....

So, I thought maybe a breaker had tripped. Checked the 5ers panel: all breakers ON... but I opened and re-closed all of them anyhow - you never know... no change: appliances still OFF. Went to the power pedestal (operating on the 50 Amp Service) and checked the breaker: it was ON but I opened and re-closed it anyhow. Still no change: appliances still off.

Went back to the 5ers panel and stared at it for a while... noted that all of the appliances that were OFF were fed by breakers on the right side of the panel. Got out the Volt Meter and started troubleshooting. First checked the Power Pedestal: 120 volts on each leg. Then went to the 5ers panel: found 120 volts on one leg and 0 volts on the other leg.

So, if there's power at the pedestal and no power at the 5ers breaker panel, the problem has to be somewhere between the two... Figured the most likely spot would be the Shore Power Inlet. First checked power at the end of the power cord: 120 volts on each leg: all good. Then noticed evidence of burning at one of the power prongs inside the Inlet Socket (see picture)... not good.

At that point I knew I had to take the Shore Power Inlet Socket out and see what was going on. Found a set screw on one of the power leg wires wasn't tight. The prong that was connected to that wire had brownish discoloration indicating arcing in the area. Next step was to take the whole assembly apart: sure enough, found the plastic around the prong had started to melt. Finally determined the root cause: one of the power leg wires had been inserted too far: the plastic insulation was partially in the clamp.

Over time, the insulation had gotten warm, deformed, and the clamp-to-wire connection loosened up. Arcing then developed and the connection failed completely. Thank goodness it didn't lead to a fire. When the Power Inlet was first installed at the factory, the technician probably tightened the terminal clamp just like the others: nice and snug.

Bought a new Shore Power Inlet online from Walmart (1.5 day delivery) and replaced the Inlet assembly. The installation instructions have a warning message in BOLD type: "Make certain there is no wire insulation under any terminal".

These connectors are very tricky to get right: you can't easily see the bare stripped wires and the end of the insulation when the wires are inserted into the terminals.

Hope this posting helps others that may experience intermittent electrical power problems that just don't seem to make sense. If you see any brownish discoloration at the Shore Power Inlet Prongs, check the wire terminations! Don't just tighten the terminal clamps: the wire insulation may be under the clamp - and like mine, the plastic that holds the prongs may have melted and deformed.

[Hblick48]

Like I've said since owning my first motorhome: "in order to own an RV, not only do you need to know how to change a lightbulb, you also have to be able to change the whole fixture."

Great troubleshooting...also saved a bunch of $$$ by not having to pay an RV tech.

[waynemoore]

Yikes that could have been bad. I once had one of the wires in the plug shore cable come off at the trailer end. Lost some of the 120 plugs a clear indication that one leg was the problem. Now just have to find just where it is.

[rohrmann]

Last year, we were ready to move on and when breaking down, was unable to remove the shore cable from the trailer inlet. One of the terminals had a overheated and damaged distorted the white part of the plug. Had to replace both ends. In this case, all the screw connections were tight.

[BB_TX]

Similar issues have been reported before. Not often. But enough that everyone should be aware of the possibility if they have a similar problem. And the pictures are great to show exactly where the problem may be.

[jpwhite]

Thanks much, another thing to add to the check list!

[SteveandTerri]

You’re welcome!

My first inclination when I found evidence of arcing was to just tighten the clamp that secured the wire at the offending prong. But, that would not have fixed the problem because the wire’s plastic insulation was under the clamp. Glad I took the time to take the receptacle apart and find the bad termination.

[darmock667]

I had similar problem in my venerable Winnie 37G Lost one leg of the outlets in the RV. Worked backwards from the breaker box and discovered the M/F connector had similar problems one leg was singed and I could not get it apart. I bought a new assembly and replaced it. All was good for a while but then I lost the other side of the RV. I went and checked the connector and no discoloration had occurred on the prongs. I have a ATS connected between the Shore and the Gennie and decided to pull the cover off of that. Damn could see the black overheated components. ATS was bad it seems. Not sure if it caused the original problem or not but did not have a spare on hand so I wired up the Shore power directly to the interior breaker box. (I had an external surge guard) I found the price of a replacement ATS and declined to buy it. Put in a 50 Amp female plug and I just had to manually plug in the shore power to the gennie.

My 2019 - 3950 was so poorly built I already disassembled the Male 50 amp plug and ensured everything was in good working order. Glad I did as the wires were fine however the connections were not tight. I have gradually been working through all of the electrical connections and fixing things as I go.

Good debugging job


Tom