and air conditioning run at 24 V DC. 2004 recall due to flaws in construction On March 12, 2004, Siemens admitted to problems concerning the stability of the car bodies and, as a precautionary measure, instructed all public transportation services to take all Combinos with a service distance of more than out of service. Torsion forces generated in S-curves were much higher than anticipated, leading to cracks around the articulations between the car modules. Subsequently, hairline cracks were found in the joints of the aluminium bodies, which could cause the roof to collapse in the case of an accident. The problem was acute in Combino cars that had run more . Cracks were reported on the connections between the sidewalls and the roof girders such that the safety of passengers in the wheel-less modules could not be assured in the event of a severe collision. These flaws were reported in many cities that had adopted the Siemens-Combinos, such as Düsseldorf, Freiburg, Augsburg, Erfurt, Hiroshima, Nordhausen, Basel, Potsdam, Bern, Amsterdam and Melbourne. In March 2004 Siemens Transport Systems confirmed that body-shell problems were emerging at high mileages and it advised all operators to take out about 400 Combinos that had run more than . Siemens launched a three-stage process of rebuilding the 454 modules affected. Under this process the Combino modules were reinforced to give an expected 30-year life. Potsdam In 1997, the public transportation authorities of the city of Potsdam were the first to purchase Combino cars. The advantages of its low-floor technology were stressed during the introduction. A total of 48 cars were to be bought through 2009. The order from Potsdam was of great importance for advertising the Combino in other cities. Cars from Potsdam were frequently used for demonstrations. After a short period of service, many inhabitants of Potsdam noticed noises during the operation of the cars louder than those of the previously used Tatra cars. In March 2004, the 16 Potsdam cars were taken out of service. As a replacement, several Tatra cars which had been given to museums were taken back into service. The shortage was aggravated by the fact that several old cars had been sold to Hungary just a month before. In June 2004, Potsdam and Siemens "amicably" declared that the at the time 32 outstanding cars were not going to be delivered. This decision is likely to have consequences for other cities.