If you do run your AC from an outlet, pop a voltmeter into an outlet in the van and check the voltage.
My AC was running fine on an extension cord on a 20A circuit until I checked the voltage inside the van - it was down to 102V which ended up overheating the compressor - I don't know yet if I have done any permanent damage to it yet.
Did you use a household extension cord or RV (thicker) extension cord?
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1990 Dodge XPLORER RV Van- Purchased 10/15/10 Chick Magnet !
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I have a separate electrical meter and 200A service to my garage and installed an outside 30A box connection alongside a 20A outdoor outlet. No problem for me or guest to plug in. Just wished I had a garage with a 10 ft. door to park my B inside.
2011 Great West Van Legend Sprinter B Camper Van
Visited states in an RV
I had just a heavy duty household extension cord which is where the problem lay - it was just not man enough for the current draw plus the circuit that I connected to was not straight to the breaker panel but serviced other outlets.
So now I always keep an eye on the voltage inside the van when I run up the AC.