Wasp nest in a/c unit, how would you deal with it?

A small propane torch at the nest entrance works well. I have used this method quite a few times and never had a bee escape. Never scorched wood or plastic material it was attached to.

When cool, no sun on cover, use a car wash attachment, soap dispenser sprayer with a bit of bug spray in the mix. From the ladder spray good though the little vents. Maybe from both sides. Wait a few minutes after not seeing any more wasp perhaps tap the cover with pole.
Rinse out with the hose so no soap or anything else is going to possibly damage anything in the sun.
Tap shroud a couple of times to make sure no more wasps. Some may have been out while you were spraying and return during or after.
It will be a mess to clean out of the shroud.
I like the CO2 fire extingusiher idea if it wouldn't make the shroud, and anything brittle or something.
Anyone know?

Malathion... they drop as fast as it hits them!

I like Pauljdav's answer.........it is messy but so effective. Only 1 application needed.

Give the wife a fly swatter and tell her not to get down till they are all dead.

I just realized just how far north Thompson is in Manitoba. If you don't need the trailer, I'd wait for the first hard freeze.

Is the nest under the cover? If so I would try to get the cover off.

I do not like poisons so close to my living quarters so I would be going with the shop-vac or destroy the nest with water or stick when they are least active. Could take a few days.
Maybe haul the RV to a new location every couple hours to lose the active ones.

I cry like a Baby and talk about my arthritis and poor vision and how much I worry about how my wife will get along without me and guilt one of my grown sons to take care of it. :B

Plastic or garbage bag and bug bomb would be the least "interesting" but we all have good wasp stories, so maybe make it something a little more risky for the entertainemrnt value! Lol

Also it's a wives tale that they don't fly at night. They will get you and you can bet that they are all at home waiting vs in the day where a bunch are gone at any given time.

Dynamite. Then report damaged trailer for insurance claim to get new trailer. No more wasps.