Washington Gas Light Co. yesterday reported a loss in the second quarter ending June 30 of $2.8 million (17 cents per share), compared with a profit of $4,000 in the same quarter last year (0 cents per share). The utility said the loss reflected lower gas sales because of significantly warmer weather during the current quarter.

"In the second and third quarters of the year, it is not unusual to have a loss to begin with," said Paul Young, utility spokesman. "The fourth and first quarters are normally good" because most sales occur in the winter, he said. Revenue in the second quarter of 1985 was $111.3 million, compared with $130.7 million for the same quarter a year ago. For the 12 months ended June 30, net income was $38 million, compared with $37.1 million for the previous year.

*Figgie International Holdings Inc., based in Willoughby, Ohio, yesterday reported profits increased 14.4 percent, to $13 million ($2.30) in the second quarter ending June 30, up from $11.6 million ($2.01) for the same period last year. Revenue for the diversified operating company serving consumer, industrial, technical and service markets increased to $390.7 million, up from $347.5 million for the same period a year ago.

The company said that, although it was pleased with the results in the first half of the year, strikes at two divisions and a product recall at another division held down second quarter earnings.

*Vienna-based ERC International announced net income for its second quarter of $521,000 (14 cents a share), a 27 percent increase over $410,000 (11 cents) earned in the second quarter of 1984. The company reported second-quarter revenue of $13.2 million, a 37 percent increase over revenue of $9.6 million for the same period last year.

For the first six months of the year, ERC earned $842,000 (22 cents) on revenue of $25 million, compared with earnings of $896,000 (23 cents) on revenue of $19 million for the same period last year.

ERC provides professional and technical services and products in defense, computer systems, energy and the environment, and logistics to government and commerical clients.

The Washington Corp., a Maryland real estate development and investment company based in Chevy Chase, announced net income of $1.2 million (59 cents a share), up sharply from earnings of $317,000 (13 cents) for the same quarter last year. For the first six months of 1985, net income was $1.1 million (52 cents), compared with net income of $763,000 (31 cents) for the same period last year.

*Software AG Systems Inc. of Reston announced net earnings of $990,000 (17 cents a share) on revenue of $14.1 million for its fiscal fourth quarter ended May 31. In the same quarter last year, the company earned $1.8 million (29 cents) on revenue of $12 million. For the fiscal year, Software AG Systems said it earned $5.1 million (86 cents) on revenue of $52.3 million, compared with $5.9 million on revenue of $41.1 million.

This year's data reflects a change in accounting at the company,which develops advanced information systems software products, specializing in application development and database management.

*Preston Corp. said second-quarter net income fell 34.5 percent, to $1.8 million (31 cents a share) from $2.7 million (47 cents) for the same quarter last year. Second-quarter revenue was up slightly, to $85.2 million from $82.8 million.

For the first half of the year, the company said it earned $2.5 million (44 cents) on revenue of $166.8 million, compared with net income of $3.8 million (66 cents) on revenue of $161.6 million in the 1984 half.

Preston, based in Preston, Md., is a holding company for trucking firms.

*Computer Entry Systems Corp. reported earnings of $443,000 (11 cents a share) on record revenue of $9.6 million for the three months ending June 30 compared with $281,000 (7 cents) on revenue of $6.4 million for last year's second quarter. For the first half of the year, CES had net income of $733,000 (18 cents) on revenue of $17.8 million, compared with $474,000 (12 cents) on revenue of $11.9 million for the first half of 1984.