Keep an eye on your power cable ends!

[WearyTraveler]

I learned the hard way about ensuring that the power cable ends are taken care of. I had to cut short my recent trip to New England when my automatic transfer switch stopped working. On gen, I had power. On shore, I didn’t. My multimeter showed 240v and not the 120&120 that was supposed to be on the input of the ats. I spent a couple of hours calling local (couple hundred mile radius) RV dealers. Most responded that they’re booking appointments 2 months out. I found one that’d help me that day.
The RV tech showed me where the ground / white wire had come loose from the screw and was periodically disconnecting. It had finally come completely out and had fed 240v into the ats and fried the motherboard of the ats. Don’t ask me about the specifics - that’s all I understand. $700, a repaired plug, and a new ats later I was on my way. I spent a night in their lot on shore power - all was well. I stopped overnight on shore power at an RV park - all was well. I got home and hooked up to my shore power and had no power. Gen power worked. I had an electrician buddy look at it. He discovered that a different plug end had the ground loose and periodically in and out. It actually got so hot it melted the rubber (?) insulation inside the molded plug. I’m waiting on new ends from Amazon to see if I fried the new ats.

Moral of the story? Those molded power plugs are pieces of crap. Replace them immediately if they start to separate or loosen.

[lwmcguire]

Over the years 30 amp plugs were notorious for melting

50 amp not so much unless damaged

For others troubleshooting

240v hot to hot is correct as the OP. Noted

120v to ground and neutral is normal from each leg

Not getting 120v to neutral indicates an open ground