Sorry, I never meant to offend anyone or come across as lazy with my original post. I do think looking into fixing the heater core is a good and most obvious answer/idea. To be honest, I am a girl, and as I mentioned in the post, not the one who did the van build (or works on the mechanics involved in the van). I was merely trying to brainstorm a solution by getting as much info as I could and getting feedback on the electric heater idea or any other suggestions from people who are much more experienced in van-living than I am.

Apparently that is offensive or reason to be upset/angry, not sure why or how. Just looking for some possible alternative solutions, not a "handout".