The National Highway Traffic Safety Admin. is issuing an appeal to owners of vehicles caught in a massive Ford Motor Co. cruise-control switch recall to have their dealer disable the feature until the auto maker makes sufficient replacement parts available in June.

Ford has been issuing recalls to fix the defective deactivation switch since 1999. The number of vehicles affected now is more than 9.6 million and includes some of the auto maker’s highest-volume products. About 220,000 vehicles were recalled for a second time earlier this month.

“We want people to bring those cars in and get the switch disconnected, because until those switches are taken out they are at risk for fire,” NHTSA’s Karen Aldana tells Ward’s. The safety group has received 60 complaints of alleged vehicle fires, as well as some dwelling fires, related to the defective switch.

The fires reportedly have occurred both while the engine was under operation and when it was turned off. It does not appear to matter if the key is in the ignition or whether drivers even use the cruise-control feature.

Aldana says the defect puts owners’ homes and lives at risk if the vehicle is parked in a garage. To date, no injuries or deaths have been reported.

Officials with NHTSA and Ford speculate some vehicle owners are aware of the recall but are waiting to visit their dealer until Ford has a sufficient supply of replacement parts in June.

Some 5 million Ford, Lincoln and Mercury vehicles with the defective switch have been fixed, leaving another 4.6 million cars and trucks still vulnerable to fire, a NHTSA spokeswoman says, thus the consumer advisory.

“People don’t want to lose the functionality,” so they’re waiting, says Ford spokesman Wes Sherwood. “But we encourage people to bring (their vehicles) in.”

Sherwood estimates Ford has notified owners of the affected vehicles through upwards of five different mailings. “That’s well beyond the legal requirements,” he says.

Due to the parts shortage, Ford is disconnecting the cruise-control switch as an interim fix. Dealers can perform the service quickly and owners do not have to leave their vehicles, Sherwood says. The permanent fix entails the installation of a new, universal wiring harness.

Sherwood also says Ford is working with a number of suppliers to build an inventory of the part, including the switch’s original manufacturer, Texas Instruments.