how to get rid of bumble bees

WD-40,, give the nest a shot,, won't kill all of em but they don't like the smell and wont come back!!
Also Hot glue fiberglass screen material around the openings..

Move to California.
That get rid of snow shoveling as well.
Bad part - you will find more spider webs in burners.

No mistaking a bumble bee since it's about the size of your thumb. Bees, wasp and yellow jackets are small, about as big around as a pencil. A bumble bee's sting feels like you've been his with a ball ping hammer, or at least that's how they feel when stung in the face/head.

The guards referenced above work against any of them.

If it's wasps floating around, grab a paper lunch sack, crinkle the top and hang it in that area. They will think it's a hornets nest and leave. Weird, I know...but it works.

Could be/most likely carpenter bees.
Screens about the only way. If you are sitting still you can buy or make carpenter bee traps. The look like little bird houses, with a specific size hol drilled at angle upward in sides. In the bottom another hole which allows them to fall into or descend into a pint jar affixed to the bottom with a hole in the lid. Simply unscrew to empty. we caught a great number in traps here this spring.
Still the screens would be the best way. I know mfg says not to block airflow but the screens I saw recently ahd good silicone type rubber gasket to go against coach and pretty large openings in sturdy stainless grid.

Run the furnace?

Is it really bumblebees, or is it yellow jackets? Or honeybees? If they really are bees, and not yellow jackets (which are striped like bees but are actually related to wasps), then the bee removal service is the way to go. If they are yellow jackets, you may need to shut off the gas and do some spraying. In any case, after they are gone, good idea to get those screens.

It's wonderful that you have bumblebees! So many native pollinators have died.

Do they have a nest in uour RV, or are they just attracted by furnaces smells?

If it's a nest, look online / in the yellow pages / on craigslist for a bee removal service. It will probably be free, as the bees are sold to those who need them.

If they are just visiting for the fumes, turn off all propane for a couple of days. Your fridge will stay cold and the bees will move on.

Vent screens.....come in various sizes/designs....available at any RV Parts Store Or on-line