If you mean 4,000 watts that seems high. I believe our space heater is 1,500 watts. We use it all the time when cool and it works fine. If you were running the inverter at the time you turned this large heater on no doubt tripped the inverter breaker. Find your inverter box, not the control on the dash and look for a breaker switch. In the future use a 1,500 watt heater and do not run even that on the inverter. Generator should be on or plugged into shore power.
I think 4,000 watts is about 35 amps and for sure that will overwhelm the inverter.
Country Coach 42' Affinity
2013 Jeep Wrangler Unlimited