REMOVING TAPE, CLEANING, AND REMOVING OLD GLUE AND GUNK
When I tried to peel mine off, it came off in little, chippy, sticky pieces. Which stuck to my fingers. Which then stuck to the garbage bag. Which then stuck back onto my fingers. ARGH! Then I got smart!
Starting at the bottom of my section of semi-disintegrating foam tape, and using my shop vac, I used the nozzle (without any attachments) to lift the tape and sucked it into the vacuum cleaner. Use the high setting so it doesn't get stuck in the hose. Use a dirty canister so the dust renders the sticky stuff powerless.
Acetone (cheap nail polish remover is almost straight acetone) applied on a cotton pad to the sticky stuff will remove it. Get a good quality pad not a cotton ball or you'll be shedding "fluff."
I worked my way up to the commercial cleaners rather than use some of the household stuff. TSP (trisodium phosphate - available at hardware stores in the painting
department - or any Canadian Tire store) will degrease and clean a lot of the built-up, day-to-day grime. I like the powder better than the ready-mix spray because I can mix a stronger solution. I used the same technique as Alf S.: scrub it on then rinse it off. Rinsing is important because TSP can leave residue. The easiest way I found of rinsing was to get a spray bottle, start at the top and let it run down to a bunch of old towels. Remove your cushions first.
If there's any mildew or mould (black stuff), you'll need a strong bleach. Don't mix your cleansers - bleaches, ammonias and other chemicals react to one another. Wait until the TSP or other solvent is dried before you start with a different chemical / cleanser. And don't knock yourself out with the fumes - use a fan, or all doors and windows
open on a breezy day, etc.
Removing Old Glue and Gunk:
Practically everything that goes on somewhat permanently has a solvent to take it off. Acetone works for a lot of the sticky glues. Rubber cement remover works for contact cement. Paint stripper (PolyStrippa or Poly Super Strippa) or brush cleaner (Poly Clens) removes old paint, although try the Shop-Vac technique first because you can often remove the bulk of the paint if it's chipping by vacuuming it well. If you have thick paint to remove, get the gel variety because it will adhere to the paint and you can leave it "soaking" to soften it. I'd apply the Poly Clens with a dripping, saturated cotton pad and have a paper towel handy to wipe up the spills. If the stuff was coming off in little sticky balls, I'd remove it with another cotton pad. I went through a lot of cotton pads. When finished, don't forget to rinse with a mild cleanser. For silicone you can try and work some water around the edges and peel or scrape it off. If it's not budging, scratch the surface of the sealant / caulking and apply Silicone Sealant Remover (Silicone-Be-Gone), then come back and keep scratching. Warning: This is labour-intensive so peel it off if you can. I used a brass brush (like an oversized toothbrush) a lot, both for removing the paint and for removing the sealants. Get these at the dollar stores - often 3 to a package for a buck. The stainless steel ones work, too, but can leave grey marks which will also have to be cleaned off.
Jon, by the time I got to the back of the unit (looks like yours in the picture you posted with the two strips of tape below the windows
and black gunk accumulated around it) I had a system. I'd quickly give it a bristle brush and TSP cleansing, rinse it, dry it, then move to the Poly Clens and brass brush with VIGOROUS scrubbing. Once that was rinsed and dried, if there was any contact cement there I'd use the contact cement cleaner. For the really old, dried gobs of contact cement I'd put the solvent on a cotton pad and let the saturated pad sit for a bit (overnight, even). If there was any mildew or mould left after all that, a bit of straight bleach on a cotton pad left on for an hour (or overnight) usually got rid of it. A final rinse with a mild or great-smelling anticbacterial cleanser got rid of any chemical smells.
NOTE: This was for a restoration-type cleaning. Don't think for a minute I do this every year. I had a trailer that had ensolite that looked for all intents and purposes almost completely destroyed in parts. So much so that the previous owners tried to mask the gunky stuff by covering the whole dang thing with spray granite paint. Not everyone will have to do this level of cleaning. To me, it was better than trying to replace the ensolite. Painting over it wasn't an option because the surface wasn't properly prepared to accept paint (which I found out first hand when all the blue granite paint started flaking off). Ensolite is pliable, stretchy and shrinks and expands depending upon the temperature. Paint does this too, but not at the same rate as the ensolite, so that causes it to flake off. If you ever do want to paint, you need to pick a paint that works on plastic.
SAFETY TIPS: Put solvents in small metel cans (like pop cans cut in half) rather than plastic cups. They melt plastic clups. Solvents will also melt all but the heaviest rubber gloves (and sometimes even those). Don't even think of doing this with artificial nails! I wore eye protectors (like plastic glasses). If this stuff splashes, you hands are already covered in it so you're toast. Use a fan or other method of ventilating. If you use a pop can for anything, make sure it looks different than the pop can you're drinking out of. It's so easy to grab one and....
(Thus endeth the lecture.)