Sunday, January 29, 2023


RVelectricity: Cause of 30-amp twist-lock failure

Hi Mike,
Our plug melted at a Wisconsin state park campground. We thought someone was burning plastic plates. We could smell it. No idea it was our plug. Image our surprise when we saw this. So lucky we didn’t burn down our camper. Everything still works in our camper, the only thing that got damaged was our decorative outside lights (we use Christmas lights).

The questions I have for you: Can my husband fix our cord with a new end (see photo of what we bought) and what do you think caused this meltdown? FYI, it did pour rain on us that weekend. Could it have been a surge, or something else?

Any answer would be really helpful. I am really paranoid now of what could happen to us. Our camper is a 2012 FunFinder, 30-amp.

Thanks. —Carlotta

Dear Carlotta,
Glad nothing really bad happened, and thanks for the great pictures. We’re all going to learn something today….

Yes, this can be a DIY project if you’re careful

Yes, he can replace it himself as long as he’s careful to follow the instructions to make sure the correct color wire is terminated in the right terminal. And be careful not to over-tighten the screws or leave any wire strands hanging out.

However, you’ll most likely need to replace the male inlet on the side of your RV, as well, since there was so much heating from the plug contacts. That amount of heat likely damaged the matching male connector and then it will be déjà vu all over again.

Did you lock it up?

There is no locking ring on this plug. Hopefully you were able to salvage the existing cover with the locking ring. So, if there was no external locking ring on the original plug it won’t be weatherproof and can twist out of the inlet. Both things can cause this failure.

Do the twist!

Have you been twisting the plug properly to lock it into place? If you don’t do the final 1/8” twist to seat the plug it won’t have full electrical contact area and can overheat.

Keep it clean (and non-oxidized)

Also, did you use contact cleaner on the connectors at the beginning of the season? That’s needed for all RV connectors that are exposed to the weather. I highly recommend DeoxIT D5 for all RV connections. Yes, it’s a little pricey but you only need a spritz of it to clean off existing oxidation and prevent future corrosion.

It’s not a surge

Finally, a power surge from a nearby lightning strike would not cause that type of damage and leave everything else in your RV operational. The failure was most likely caused by oxidation of the contacts. But it could also be caused by loose screws in the plug, plugging it in wrong by not twisting the plug to lock the contacts, or excessive current from running air conditioners constantly (which shouldn’t be possible if you’re connected to a properly installed 30-amp circuit breaker).

Look for signs of trouble

I would also suggest that everyone periodically inspect their shore power connections to make sure nothing is overheating, especially if you’ve been running your air conditioner nonstop. If the plug or wiring feels hot to the touch, then something is wrong. You need to address the problem immediately or you could cause a fire.

Let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at For more info on Mike’s qualifications as an electrical expert, click here.

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1 year ago

The Hughes Autoformer should eliminate any low voltage electrical system damage to RV’s. It has been around a long time and the manufacturer information is pretty solid.

Mike Sokol
1 year ago
Reply to  Ken

Low voltage should not cause this kind of failure. The only electrical appliance in an RV that will increase its current draw with low voltage is the air conditioner. And if the RV current increases beyond 30 amps for a sustained time, the 30 amp circuit breaker should trip. UL lists that connector for 125% of rated current without overheating, so a properly installed and maintained twist lock connector should not overheat. My gut feeling is that many times the weatherproof seal on the locking ring fails and corrosion sets in.

Lee A..
1 year ago

I really appreciate your knowledge and wilingness to share it with others. I read your reviews of the SmartPlug awhile back and did the install on my RV. Since using it now for about 6 months I think it is far superior to the old twist lock plug and am happy I made the switch. I am a bit surprised that you did not suggest it to Carlotta since they were going to have to replace the burned connectors anyway.

Tommy Molnar
1 year ago

When stuck in Houston last year (all summer), the a/c was on 24/7 for months. The plug felt warm (fridge and water heater on as well), but it was in the 90’s 24/7 as well. The water heater didn’t come on all that often, but the fridge was on all the time, fighting to keep our chow cool. Now we’re headed down there shortly for yet another week (GASP!) Should I be worried about this situation? Our shore power cord is permanently attached inside the trailer (the old style).

Gary Reed
1 year ago
Reply to  Tommy Molnar

When operating my A/C continuously in high ambient temperatures I run the hot water heater on gas as well as the refrigerator. I minimize the electrical load of the RV to provide as much current to the RV A/C. We are on a 30 amp system. If you do not already have one a good quality surge protector with a voltage monitor system would be a good investment. The surge protector with voltage monitoring will shut down the electric system to the RV if campground voltage at the pedestal drops to unsafe levels.
In crowded RV parks where everyone is running their A/C this can reduce pedestal voltage to unsafe levels.

Mike Sokol
1 year ago
Reply to  Gary Reed

I agree completely.

Tommy Molnar
1 year ago
Reply to  Gary Reed

Good idea, Gary. We’re headed back down there (UGH!) in another week and using the gas for the fridge and the water heater (which almost doesn’t need to be turned on at all!) will be the plan. Besides, I’ve always found that the gas part of both the fridge and the water heater seem to work better than the 120. Thanks for the tip.

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