DETROIT – General Motors plans to close its Detroit-Hamtramck Assembly plant for four weeks in June to upgrade the facility’s capacity to produce Chevrolet Volt vehicles and prepare to assemble the 2013 Chevrolet Malibu sedan.

The automaker said the retail supply of Volts will be restricted during the next three months before the company resumes production. Coupled with already low dealer inventories and strong demand, the suspension of production, will result in limited availability and reduced sales in June and July. 

As a result of the plant upgrades, planned Volt and Opel Ampera (the European version of the Volt) production capacity this year will increase to 16,000 units, including exports and a fleet of several hundred demonstration units sent to U.S. dealers. In 2012, global production capacity is expected to be 60,000 vehicles with an estimated 45,000 to be delivered in the United States. GM said it’s taking this action due to high customer demand for the vehicle.

“The Volt will be available to customers nationwide by the end of 2011,” said Cristi Landy, director of Chevrolet Volt Marketing. “By taking the time to reconfigure the plant, we will be better able to meet the tremendous consumer demand.”

The 2011 Volt was launched in California, New York, Connecticut, Maryland, Michigan, New Jersey, New York, Texas, Virginia and Washington, D.C.  The Volt will be available nationwide and in Europe, China and Canada by the end of this year.

Production of the all-new 2013 Chevrolet Malibu will begin next year, according to the automaker.