 GM halted production for about one month at the Detroit / Hamtramck Assembly plant by mid June 2011 to complete some upgrades, including the installation of new tooling, equipment and overhead conveyor systems throughout the facility. These upgrades allowed GM to triple the rate of Volt production and prepared the plant for 2012 Volt and Ampera production. After the plant retooling, the production rate reached 150 units per day four days a week by August 2011. The Volt plant was also down during January 2012 in preparation for building the California lower-emission version. A four-week shutdown due to slow sales took place between March and April 2012. GM said it had around 3,600 Volts in inventory and needed to reduce dealer inventories as production is expected to meet market demand. GM also extended the traditional two-week summer vacation by an extra week at the Hamtramck plant. GM closed its Detroit-Hamtramck plant from September 17 until October 15, 2012, affecting roughly 1,500 workers on downtime while the plant was retooled to assemble the all-new 2014 Chevrolet Impala alongside the 2013 Volt. This was the second time in 2012 that GM has halted Volt production.
