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New York City Transit Hybrid and CNG Transit Buses: Interim Evaluation Results - page 42 / 64

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  • Electric propulsion systems maintenance costs—These costs pertain only to the hybrid buses at Mother Clara Hale. Most of these maintenance issues for the hybrid buses had to do with troubleshooting the hybrid control system and learning to diagnose electric propulsion system failures. Some of the problems reported in the maintenance system included the PCS cooling system, triple pump, filters, traction battery, and traction motor. Troubleshooting work orders in this category included “won’t start” and “check” or “stop” hybrid electric vehicle HEV lights. During the evaluation period (October 2004 through May 2005), the hybrid fleet has had several single battery replacements including a few single battery replacements for the hybrid study group. This hybrid fleet of 125 has not incurred a roadcall attributable to the traction batteries. BAE Systems is investigating historical replacement actions to determine root cause and consider whether an opportunity exists to modify procedures or energy storage system monitoring software to improve overall system performance and reliability. This analysis from BAE Systems has been promised for the final evaluation report for the order of 125 hybrid buses.

  • Non-lighting electrical systems maintenance costs—These costs include general electrical maintenance other than lighting including charging, cranking, and ignition systems. The CNG buses had maintenance costs 58% higher than the hybrid buses. The CNG buses had issues with the starter, the main power control and communications systems. The spark plugs on the CNG buses have been an issue with failures as early as 4,000 miles. The CNG engines now use four iridium spark plugs costing $240 for the set. DDC paid for the first set of these iridium spark plugs as part of the CNG engine campaign and now NYCT will be paying for the subsequent changes on a 24,000 mile interval or approximately once per year. Only one set of these new spark plugs were accounted for during the evaluation period, and more are expected in the final results report. NYCT reports that the new spark plugs are working much better so far.

Issues for the hybrid buses in this category included the voltage regulator, alternator, and wiring.

  • Air intake system maintenance costs—The CNG buses had maintenance costs 38% higher than the hybrid buses. There were no major problems or issues for either fleet in this category.

  • Cooling system maintenance costs—The CNG buses had maintenance costs 13% higher than the hybrid buses.

  • Transmission system maintenance costs—The hybrid buses do not have a transmission. The CNG buses did not have any significant transmission repairs during the evaluation period.

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