Lately when I plug my camper into campground 30 amp current (or when I use a 15 amp adapter for camper current while parked at my home) after a while, often with the heater on, the lights begin to flicker and then dim, the heater fan slows, etc. After some minutes (and the heater off) I get full brightness back when I switch on the lighting. I have a 2003 27' Class C Jayco. Any of you electrical smart folks out there have an idea(s) what is going on? Please let me know; I'm stumped.