grey water tank cracked and shore power plug melted

[JVess]

And the song goes "if it weren't for bad luck I'd have no luck at all". Early spring while camping in Florida our grey water tank started leaking. I paid an RV repair person to patch the crack. The repair is still holding.
Last month went camping and on last day I heard a loud burping sound and water came running out of under belly. A new crack has formed on top of tank and only leaks when full. While investigating the water leak today I also noticed the lights (12volt) were dim. I checked around and discovered the rv did not have 110 power (camper is at an enclosed storage facility with power). The shore power plug at camper has melted and it cannot be removed.
Two questions:
1. Has anyone heard of a power cord melting at plug in to camper and if so do you know what caused it?
2. My Avalanche has one bottom cross brace that supports the grey and black tanks. The tanks are 48 gallons, it seems there should be a minimum of two.

[Hercules1978]

I can't answer the frame question, but the melted plug sounds like low voltage.
As the voltage drops the amps (current) increases to maintain the demand. This causes extra heat in each connection.

The power formula is P (watts) = I (volts) x E (amps)

120V X 30 amps = 3600 watts

If the voltage drops by 10V you end up with
3600W/110V = 32.72 amps
Now you are 2.72 amps over your rated capacity.

[JRTJH]

...
2. My Avalanche has one bottom cross brace that supports the grey and black tanks. The tanks are 48 gallons, it seems there should be a minimum of two.

I can't say for sure how Avalanche supports their tanks in the 2011 models, but Cougar is built in the plant a couple of buildings down from Avalanche and they have gone to an "unsupported" tank installation system. Your Avalanche may be an "adaptation" of the "old system and the new system" or who knows ???? Here's a picture of how the current model Cougar tanks are laid into the frame and supported by a flange around the tank rim. There are no support straps under the tanks, they "float" in the "belly cavity"....

It's possible that your tank supports are designed to only have one strap. Your dealer would probably be your best source of information (assuming his service department has experience with more than one model of Avalanche and has worked on the tank system in that year model) In the RV industry, not a lot is "standardized" or "the same on every model that goes down the line"..... Yours may be different than the one that was built before it and/or after it.....

[WaltBennett]

X2 low voltage, although you could have had a transient (as in lightning strike nearby). Better check out all the electronics.

[hankpage]

Corrosion or dirt on the outlets contacts or the plug can cause arcing and the heat that melted the plug. You will have to turn off power at pedestal and replace the plug and outlet. A light coating of dielectric grease on the new plugs prongs can prevent this from happening again. JM2¢, Hank (You can get the dielectric grease at an auto store in the bulb section)

[JVess]

Great information... we have had a low voltage issue at our storage facility. Our surge protector did not show any errors. We have a Progressive Industries protector.

I am adding two additional rails to support the tanks.

[Bob Landry]

I seriously doubt this is a low voltage issue. The prongs on the power plug have arced and burned over a period of time creating a high resistance connection and generating a voltage drop and overheating, causing the plastic material in the plug and the power inlet to fuse together. It was probably the result of either plugging in with the breaker turned on or bad contacts on the CG's power pedestal. That's why many have switched to running off the 50A plug using an adapter. They get less use and abuse.

[JVess]

Since the surge protector did not log a low voltage error I think Bob maybe correct. If he is correct do you think I may have additional issues with wiring or electronic components inside trailer? I guess I will know for certain after the repair is completed.
Thanks again for the help!!!