MELROSE — A South Bronx subway station is plagued by men who jam the MetroCard vending machine cash feeder and leave straphangers no choice but to wait on long lines for a clerk or pay them for an illegal swipe, the MTA and locals complain.

At the 149th Street/Third Avenue station — a busy hub that serves the 2 and 5 subway lines — groups of young men regularly break the machines so they can profit from the lucrative scam, MTA officials and locals said.

“Over 80 percent of the MetroCard vending machine service calls at this station are a result of vandalism,” an MTA spokesman said, adding that the agency is working with the NYPD Transit Bureau to resolve the problem.

MTA staff at the station said agency technicians recently had to fix one machine four separate times on a single day after the teens kept jamming the cash payment slot. But without police constantly on watch, and with the booth clerks unable to fix the machines themselves, staffers said there's nothing they can do.

“These guys, they call them ‘swipers.’ They jam up the machines,” said an employee who declined to give his name because he is not authorized to speak for the MTA. “If we see them we call the cops. We should have police officers in the station around the clock.”

But in the meantime, frustrated commuters say they are tired of constantly being thwarted by MetroCard machines that accept only coins or debit cards — which some said many in the community do not have — while being bombarded by swipers.

“People do not have bank accounts, let alone debit cards,” said commuter Taneesha Crawford, who uses the station, "It’s an easy set up to catch people who hop on the train.”

“It’s been happening a lot,” added Lidia Thabit, 22, a student who usually buys weekly cards or carries change to avoid the problem, which she said is frequent at several stations in the Bronx. “It’s very inconvenient. Who carries around $2 in quarters all the time?”

Frances Davide, 36, who was taking her son to a doctor’s appointment, said she was too late to walk to the opposite platform to the staffed booth to buy a card, so she decided to pay for a swipe.

“It’s the only option I have,” she said, “If this was Manhattan they would fix it right away.”

On a recent visit, machines on both uptown and downtown platforms warned, “no bills accepted” and “single ride tickets only.”

Young men offered riders who couldn't get MetroCards at the machine, “$2 for a swipe?”

Niko, 17, who spends his afternoons standing by the machines, admits he alternates between several unlimited MetroCards to swipe commuters in.

“We just swipe them in. Most people go with it. At the end of the day it’s cheaper for them that way,” said the teen, whose last name is being witheld because of his age. He justified his crime by comparing his $2 fee with the $2.75 a single ride normally costs.

Niko denied purposefully jamming the machine, but said he knew that he was breaking the law.

“If they catch you, they arrest you. But we’re too fast for them,” he boasted.

Iris Walker, a Jehovah's Witness who canvasses this station twice a week, said she sees the same scene every time.

“It’s good business for them,” she said of the swipers. “This is how the new generation does it.”

Some commuters refused to cooperate in the scam.

“You can get locked up for that,” said Daniel Torres, 30, a medical assistant, who instead stood on a line of about fifteen people waiting at the station’s teller. “But we pay too much for this. We should get better service.”

Many riders complained the MTA is not doing enough to solve the problem.

A commuter who only gave his name as John vented his anger against the MTA.

“These machines suck — they’re always breaking down,” he said, adding that sometimes the machines will take cash but not release MetroCards. “The MTA, they don’t care for anyone. Anywhere where people of color live, people who live in poverty, they don’t service it.”

Some riders, like Natasha Edwards, 26, came to the agency’s defense.

“It’s not the MTA. It’s people who are messing with the machines,” she said.