A day after federal safety regulators warned owners of recalled vehicles with defective airbags to “act immediately” and get them replaced because they could explode, consumers on Tuesday were left grasping for answers.
A link from the website of the National Highway Traffic Safety Administration that lets owners look up their car by vehicle identification number did not respond all day. Calls to an operator on the agency’s hotline — 1-888-327-4236 — were routinely put on hold.
And many owners who tried to get their cars fixed were turned away because the parts, made by the Japanese supplier Takata, were simply not available.
At issue is a faulty propellant inside air bags that is unstable and can explode even after a minor accident, sending metal shards flying into the cabin. The defect has been linked to at least three deaths and more than 100 injuries.
David J. Friedman, the deputy administrator of the agency, said that it decided to issue the warning on Monday after receiving test results from Takata on returned airbags in recent days, and out of concern that owners were not getting their cars fixed.
Graphic: Takata Air Bag Recalls: Affected Vehicles
In all, more than 14 million vehicles from 11 automakers have been recalled for the defect, most in the last two years.
The agency’s balky website was set up to be a nationwide clearinghouse for recall information on vehicles registered in the United States. On Tuesday, most functions meant to serve consumers, including looking up the recall information and alerting the agency to potential problems, were unavailable.
“N.H.T.S.A. is experiencing intermittent network issues that are making some functions on SaferCar.gov temporarily unavailable,” the agency said in a statement, adding, “We apologize for the inconvenience and encourage you to try back later.”
Most automakers have their own sites that allow consumers to search for recall information using their vehicle identification number. The automakers covered in the warning included Honda, Toyota, Nissan, Mazda, BMW, Chrysler, Subaru, Ford, Mitsubishi and General Motors. Late Tuesday, the agency revised its list to include five more automakers and raised its total by a million vehicles to 6.1 million.
Addressing the confusion and frustration among car owners, Senator Bill Nelson, Democrat of Florida, urged automakers to make loaner cars available, an option that G. M. offered to owners of 2.6 million older cars affected by recent recalls over a defective ignition switch. Mr. Nelson also criticized the decision to limit some recalls to areas only with high humidity.
In June, automakers, with the approval of the safety agency, recalled 900,000 vehicles for the airbag defect, but only in Florida, Hawaii, Puerto Rico and the United States Virgin Islands. Honda expanded that recall to an additional 2.4 million vehicles registered or first sold in Alabama, Georgia, Louisiana, Mississippi, South Carolina, Texas and California.
“These automakers should take the additional step of immediately offering loaner cars or rental car reimbursement expenses for consumers that cannot get their cars fixed in a timely manner,” Mr. Nelson said in a statement.
For many owners, heeding the agency’s advice to act immediately was impossible. Dealers have been telling frustrated car owners to expect to wait many months before their airbags can be replaced.
Daniel Gluck, a civil rights lawyer from Honolulu, said his Toyota dealership’s designated repair shop, Motor Imports Toyota, had said there was a 90-day backlog for the parts necessary to replace the airbag on his 2003 Corolla.
Mr. Gluck, who has two children, said the shop had not yet suggested deactivating his airbag, but he welcomed the option.
“I’m surprised that there’s such a long wait for the parts, given the stated urgency of the repair,” he said. “To be honest, it’s probably fine, but I’d certainly like to get it fixed.”
Mr. Gluck was not alone in his concern. His dealership was overwhelmed with calls on Tuesday.
“It has been superbusy — started yesterday, nonstop, 7 a.m. to 6 p.m.,” said Janelle Castro, who works in the dealership’s customer care center. “I’m going to say that if we take in 1,000 calls a day, maybe 900 of them are recalls.”
Takata did not respond to a question about when its parts would become available. Shares in the company dropped 23 percent in Tokyo on Tuesday.
Toyota, with about 877,000 affected by the warning, said it was sending “additional stock of available parts” to distributors along the Gulf Coast “and asking them to prioritize deliveries to dealers in the coastal areas of high absolute humidity,” a spokeswoman, Cindy Knight, wrote in an email.
Toyota said that if replacement parts were not available, it would disable passenger-side airbags in areas of high humidity, leaving a note not to ride in the front passenger seat, a policy that safety regulators endorsed.
Normally, automakers may not disable airbags, but Mr. Friedman said that he did not see it as a problem in this instance. “It is not clear that they need permission under the law because it is a broken system,” he said.
Ryo Sakai, a spokesman for Toyota in Tokyo, said Toyota’s policy was logical, stressing that it was urging car owners not to use the front passenger seat.
He said the parts shortage was confounded by the fact that the part in question — the airbag inflater — was designed specifically to each model and using other suppliers was not an option.
“As there are no replacement parts from other suppliers available, we are working with the supplier to ready the parts as quickly as possible,” he said in an e-mail.
No other automakers say they are considering disabling airbags. But Toyota’s plan raised concern among other safety experts.
“It’s a very controversial decision,” said Allan J. Kam, a former senior enforcement official at the safety agency who is now a consultant in Bethesda, Md. “If you disable the airbag, it won’t go off in a collision where it could benefit or save the consumer from a more serious injury.”
He added, “A better way is for the automakers to stop consumers from driving these cars, and give them loaners.”
Most automakers, including Honda and Toyota, said that they would decide on whether to give out loaner cars on a case-by-case basis. Honda emphasized that it was not part of the offer.
Honda, which has about five million vehicles affected by the recent warning, is taking a different approach on the recalls, sending out notices only as parts became available. It acknowledged that some drivers would not receive notices for weeks or longer.