The failure of an electronics firm to tell the federal government that the smoke detectors it had sold could start a fire instead of warning of one has led to a $100,000 settlement of potential civil penalty action.

The Consumer Product Safety Commission announced yesterday that the Pittway Corp. of Northbrook, Ill., doing business as BRK Electronics, had agreed to the payment and to intensify efforts to locate the remaining half of the estimated 115,000 smoke detectors involved. The company already has cooperated with the government by voluntarily recalling some 60,000 of the smoke detectors.

The CPSC had charged Pittway with failing to report a defect in the BRK SS749 series smoke detectors "which could cause such products to fall to operate and, in certain instances, to catch fire."

The commision said the defect consisted of the use of incorrectly rated resistors in the detectors, which were sold under several names.

The units subject to recall are 110 volt AC powered detectors are involved.

The detectors, some of which were built with ordinary power cords and others with wiring designed to go directly into electrical wiring, were marketed by BRK, American Machine & Foundry (AMF), I-T-E Imperial Corp. and Sears Roebuck and Co.

Following are the model numbers of the units affected:

BRK: SS749AC, SS749ACS, SS749L, SS749SL.

AMF: 2000AC, 2000ACL.

I-T-E: it01-AC.

Sears: 9-57049, 9-57047, 9-57048.

The CPSC urged consumers to check for model numbers on their units, but only after electrical power to the unit has been turned off at the fuse box or circuit breaker.

Owners of Sears units should contact their nearest Sears store, which will arrange for inspection and free replacement of the defective units.

Owners of any of the other units should contact BRK to obtain a factsheet giving specific criteria for identifying potentially defective units and instructions for replacement.

For additional information concerning the recall consumers should contact BRK Electronics, 80 McClure Ave., Aurora, Ill. 60507, attention: Dennis Wm. Clair, project 749 director; or call toll free 800-323-9005 and ask for the project 749 department.