Hi Kathy and Kristen,
I think I solved it! I finally managed to find a proper service manual online, instead of the usual owner's manual, and discovered how to get the case open - only 2 screws, but one is located in a tiny channel right behind one of the castors. You need a screwdriver of at least 7 inches shaft to get to it! I'd never have spotted it without the manual.
Anyway, long short, it turned out that the internal hosing is so old that it's breaking up. I think it must have fractured minutely, giving the problems. I've replaced most of it this afternoon and we seem - fingers crossed - to be back in business.
For anyone in the same predicament, this site is totally ace - it has proper service manuals for pretty much every type of oxycon on the planet -
http://www.frankshospitalworkshop.co...e_manuals.html
Where would we be with out the WWW and how did we ever manage before it arrived?
Many thanks to both of you kind ladies for trying to help. It does make a difference knowing that there are such nice folks around.
