I have these exorbitantly expensive built in through the wall a/c units.
They are so expensive mainly because they are supposed to go on and on and
on (and on)

They have virtually no features and are exceptionally old fashioned but the
replacement units (made by the same manufacturer or, - only, - one other
which will fit into these sleeves) are identical and equally old fashioned

There is a company around me which specialises in coming out free and
telling you that you need new units and that they will sell you new units
for some extraordinary amount of money. There used to be a guy in our
building who would service them EITHER cheaply by doing a quick clean job on
them so that 13,500 BThU units which actually give out about 6000 can give
out possibly as much as 9000. OR he could do what he called a more
appropriate job which we were putting off which involved taking the hwole
slip-in unit downstairs and steam-cleaning something underneath them to
restore the whole functionality of the unit, which we really need

He has departed for various health reasons. Now I have found a new company
which charges a call out charge to clean the units which doesn't actually
seem too expensive and an even smaller additional charge to do additional
units. But they seem to think that the cleaning process will take about a
half hour a unit.

Does anyone know how you steam-clean one of these units PROPERLY, which is
the difficult bit to steam clean on the underside, how important it is to do
this to get a 9000 unit back to 13,500 and how long it should take to do
this (by someone who does this every day)? I am reluctant to pay this
company the call out charge merely to be told that I need new units because
they want to sell me them. (I have been caught out that way once before when
I called the company with the largest ad in the yellow pages only to find
that they put this in BECAUSE it imparts credibility to a cowboy who will
come along and spin you a yarn about needing a new unit refurbished by him)