Well, the first attempt by Truma to replace the Domestic AC in an Oliver was a big fail...for the simplest of non-Truma reasons.
After we got the interior box removed, along with the mounting bolts, the external unit should have just lifted off.
It would not move, I mean two guys pushing from the external edge and from the inside pushing up.
Called Oliver Service, they said it was mounted with butyl tape and may be tight.
From what we could see the rear had a 1/2" thick rubberized molding piece supporting it. It wasn't butyl. Even using body shop plastic wedges we could get no play in trying to separate the unit from the 'tape' or the tape from the trailer.
We debated taking the AC apart to separate it, but that could have still been a dead end as you really need that piece and whatever is up front to come off the fiberglass and we didn't want to damage the gelcoat by try to cut between the 'tape' and the surface.
So, we put it back together and will see what Truma and Oliver can come up with.
It's possible in my May 2020 delivery cycle they were using something different than butyl tape, because it was locked in.
The unit set in the Alabama sun for its first year, but has been covered the rest of it's storage life..so not sure if sun really made much difference.
Almost like the difference in LocTite Red vs Blue.
If it was in a shop you could use a fork lift to ease the unit up, but you still have the issue of whether the tape will come with it and/or damage the gel coat.
I don't know how often Oliver Service has had to replace an AC on older units, but I'm guessing not many.
If you are having yours done, you'll have to remove the interior hold-down bolts to determine how hard/easy it comes off.
If they can work out a non-destructive way to remove the mounting 'tape', we'll give it another try.
This is an issue, irrespective of whether replacing with a Truma, Houghton or something else.
More to come, I hope....