A319 Captain experiences a crew oxygen system failure during preflight testing and informs Maintenance. Maintenance attempts to defer the oxygen indication system but the crew refuses to accept the aircraft.

Narrative

While performing the preflight O2 check I got the following ECAM indication: OXY turned amber...pressure was approximately 1;650 PSI and REGUL LO PR appeared in amber under the pressure display. I HAD SEEN THIS BEFORE. Approximately last summer; had an aircraft with the same problem. In that case; Maintenance replaced the regulator and some sensors with no effect; and the jet was removed from service. On this day Maintenance felt it was an indication problem and the intent was to defer the oxy indication. As before; when the First Officer and I donned our O2 masks; after 2-3 good breaths; the masks sucked in against our face. There was DEFINITELY an airflow problem. Took quite awhile to convince Maintenance of this; we switched airplanes and I believe the aircraft was removed from service. The first time this occurred; I thought it was just a strange; fluke 'Airbus failure'. Now that I have seen this failure twice; my concern is there may be a fleet wide problem. PLEASE NOTE: This failure is ONLY noticed if you are looking at the ECAM oxygen indication while performing the O2 check!!!!!!!!!!