The developer of The Willoughby of Chevy Chase Condominium, located in affluent Friendship Heights just outside the District, has signed an agreement to establish an initial $800,000 account to pay for properly repairing and painting the exterior of the 815-unit project.

The agreement settles a complaint filed with the Montgomery County Office of Consumer Affairs by a Willoughby unit owner. The owner charged the developer had failed to complete repairs and the exterior repainting of the complex that consists of two high-rises.

Terms of the 15-page agreement were announced yesterday by the consumer affairs office, which has been working with The Willoughby's Council of Unit Owners and the developer, Friendship Heights Associates. Friendship is a joint venture consisting of two Illinois companies, First Savings Corp., a wholly owned subsidiary of Citicorp Savings of Illinois, and First Condominium Development Co.

The exterior of the complex was painted, but, according to the settlement, the paint began to peel because of inadequate preparation. "Subsequent to the repainting failure," the settlement said, "it was determined that other exterior conditions existed at the building as a consequence of which water seeps into the individual units through windows, window frames, and other sources, and it was further determined that in some respects the exterior concrete of the building requires resurfacing, repatching and repairing as well as repainting . . . . "

The developer agreed in the settlement to commence work immediately, beginning with an engineering study to determine the causes of "paint and concrete exterior failures and water seepage."

"We are all very excited that we have been able to have this agreement signed by all parties," said Nancy Mellon, a unit owner and president of the board of directors for The Willoughby Council of Unit Owners. "And we are most anxious to have the work done."

The developers also indicated satisfaction with the agreement. "We are willing and ready to proceed with the project and put it back into the first-class shape that it should be in," said Thomas Hart, a spokesman for Citicorp Savings of Illinois.

If the repair and repainting exceeds $800,000, Friendship Heights Associates will pay the additional costs, according to the settlement, which county officials described as the largest ever negotiated by the consumer office.

Joseph Giloley, who handles housing issues for the consumer office, said the settlement shows that condominium owners have leverage to get repair work done if they act before all the units are sold. About 25 units are still unsold at The Willoughby, the settlement said.

Consumers make a mistake if they let negotiations drag on until nearly all the units are sold, Giloley said, because the developer then has less motivation to complete necessary work