A breakdown in the air-conditioning unit at Westpac's primary data centre in Sydney yesterday led to the loss of key banking services for part or all of the day.Merchant services, including eftpos and credit card processing; ATMs and internet banking all failed at around 8am Eastern time.The bank had restored merchant services by late in the morning but took until late in the afternoon to bring back internet banking services.The bank extended the cut-off for batch payments to 7pm for consumer payments and 7.30pm for payments lodged through corporate banking channels.Head of business banking Rob Coombe, interviewed by ABC Radio, suggested the problem was not so much the breakdown of the air-conditioning systems or even the lack of a back-up cooling system, but the delay in notice of the breakdown reaching the right staff.Late last year, the bank noted that it had cut the number of Severity 1 incidents it endured (a systems problem for which there is no workaround). Having recorded 30 such incidents a month in 2007, the bank had reduced that to two or three a month.