Warning to Philadelphia motorists: If you're planning to park your car on the street in Center City or University City, carry plenty of quarters or invest in a Smart Card, the Parking Authority's version of a pre-paid gift card.

The authority's executive director, Vincent Fenerty, said this week that a still-unexplained malady had struck some of the 1,044 kiosks installed to dispense parking receipts in prime curbside parking locations.

Around a week ago, Fenerty said, some kiosks began rejecting debit and credit cards.

The Parking Authority was alerted to the problem by electronic error messages from the kiosks themselves, according to authority spokeswoman Linda Miller.

"It's sporadic," Miller said. "You go to one machine, and it doesn't work, then you go to the next, and it does. . . . Or you get a message saying Kiosk 123 is not accepting credit cards, and when you send someone to look, the machine is operating properly."

Engineers from the manufacturer, an English firm called Metric Parking, have not yet figured out the glitch, she said.

The Parking Authority has paid just over $10 million for the devices, about $10,000 each. Metric was the lowest of three bidders offering similar equipment, Miller said.

"We're working on the problem, but we wanted to make sure people would have knowledge of it, so they'd have change or a Smart Card to be able to pay," Miller said. Pre-paid Smart Cards are available in various denominations at many supermarkets, newsstands, and convenience stores, as well as at PPA headquarters at 3101 Market St., Miller said.

And if someone gets a ticket for parking after a kiosk fails to honor your credit card?

Good luck.

Miller said such tickets would not be automatically discharged. To appeal, recipients would have to appear at Ninth and Filbert Streets and make their case to the city's Bureau of Administration Adjudication.