Hi Andrea
I have exactly the same problem on one of our SIRA II's.

Diff pumps off message appears but diff pumps are definitely on - how many
burned index fingers are out there!!!

Occasionally by just turning the diff pumps on and off a few times on the
rear panel of the SIRA this problem is overcome, or just reboot the
computer.  I have been know to just let the computer beep for a day or two
and it cures itself!  I'm sorry I can't give you a more technical solution
than this.

If it persists you can short out the message flag on the board in which
case you will never get a message that gives diffs off but of course you
then have to make sure the diffs are on by burning that inex finger again
and again!

Best wishes

Paul
--
Paul Kennedy
Stable Isotope Laboratory
School of Ocean Sciences
University of Wales, Bangor
Askew Street
Menai Bridge
Anglesey
United Kingdom LL59 5AB

Tel + (0)1248 388116
email [log in to unmask]

http://www.sos.bangor.ac.uk/research/stable_isotope/index.htm