The Bloomberg administration took issue yesterday with a City Council bill that would ban the sale and installation of certain car alarms, arguing that it was overly broad and could undermine police efforts to reduce auto thefts.

But during a four-hour hearing on the bill, Councilman James F. Gennaro, chairman of the Committee on Environmental Protection, proposed a compromise that would apply only to audible alarms that are motion-activated or sound for longer than three minutes.

Calling it an important step toward fighting noise pollution, Mr. Gennaro said, "Just as we took actions to reduce exhaust fumes, I look forward to exploring additional actions that the Council can take to address the noise pollution caused by all types of audible car alarms."

Council leaders later said they were still discussing Mr. Gennaro's proposed compromise and that it was unclear whether it had broad support among the members.

The move to limit the bill drew support from some administration officials, but also criticism from several advocacy groups that have unsuccessfully pressed the Council for a total ban on car alarms.

"This is already so weak as to do little good," said Aaron Friedman, project manager of Transportation Alternatives, which advocates fewer cars and more bicycles.

The Council speaker, Gifford Miller, who supports a national ban on audible car alarms, has said that a city ban would not be practical, because manufacturers routinely install the alarms as part of a car's central wiring and monitoring system. So Council leaders have pushed forward with a ban on the post-factory installation of the alarms.

City law currently allows the use of car alarms that are activated by a remote device or by direct physical contact. It prohibits the use of motion-activated audible car alarms, or alarms that sound for longer than three minutes, but because of a loophole in the law, it is not illegal to sell or install these kinds of alarms.

Council aides said that a recent survey of 50 auto shops in New York City had found that nearly three-quarters of them were still selling and installing alarms that were banned under city law.

The Police Department opposed the current bill on car alarms because they constitute a preventive measure that car owners can take to protect their property, said Howard R. Lawrence, commanding officer of the auto crime division. He pointed out that auto thefts in the city have dropped by nearly 80 percent in the last 10 years, to about 60 stolen vehicles a day last year from 300 vehicles a day in 1993.

"We are reluctant to remove any of the elements of a theft prevention system,'' he said.