The workers went on strike on April 20 seeking recognition for their union and went on fast on May 2.
Tuesday's talks involving the management, the labour board and workers failed, according to a representative of the workers.
A spokesperson for the company said the factory used to work at 97-98 per cent capacity, but had now come down to 90-93 per cent.
The company produces 900 to 1,000 vehicles a day at Sriperumbudur.
A Sounderrajan, president of Centre for Indian Trade Unions' Tamil Nadu unit, told Business Standard that the Hyundai management had not recognised the union, a registered body formed in 2007 and the only union there, and had dismissed 65 people, suspended 34 and transferred some others for enrolling as members of the union.
The management, he said, was hiring contract workers for direct manufacturing and denying leave benefits to workers.
The Hyundai spokesperson said there was no union in the company, and that of the 800 striking workers, hardly 150-200 were from Hyundai, of which 75 had already been suspended.
The spokesperson called the strike illegal and motivated by political parties, since Sriperumbudur had become a parliamentary constituency.
He added that the company would consider recognising a union of it was proved that the majority of the employees were part of it.
