If it is fixed, break it. So it goes in America’s third-poorest city. We get something that works, and the mayor insists on messing it up.

The latest apparent casualty is the Olmsted parks.

The true believers—most of them volunteers—of the Olmsted Parks Conservancy keep the city’s six-park legacy in fine shape. Every tax dollar it gets to run Delaware, Riverside, Front, South, Cazenovia and Martin Luther King parks basically buys twice as much in services, given the conservancy’s hundreds of volunteers and millions of dollars in donations. Last year, it also trained 300 welfare-to-work folks.

It might be the best buy in local government, but somebody needs to inform the mayor.

Brown funnels hundreds of thousands of dollars in shaky loans to barbershops and beauty salons yet seems ready to kick the deep-discount conservancy to the curb.

It is a great way to run the city, if you want to run it into the ground. The prospect of a City Hall with a reverse Midas touch taking over the Olmsted parks is scary enough to shake the remaining leaves off the trees. At year’s end, the city will retake control of its parks from the county. The city had paid the county $1.8 million annually for parks care, most of it funneled to the conservancy for care of the Olmsteds.

In return, the conservancy has given taxpayers upscale parks at down-low prices. Until now. It looks as if Byron Brown&Co. will slash the conservancy’s funding, strong-arm control of some of the conservancy’s jobs or simply cut it loose. It is hard to tell, the conservancy’s David Colligan said, because pinning down city officials is like trying to get a moody teenager to clean his room.

“We need them to talk to us about what the real money is,” said Colligan, the conservancy’s board president. “But it’s hard to get city officials to even return phone calls.”

If I were running the city, I would hand the conservancy a contract and a Christmas gift, not put it on permanent hold.

It is not just the Olmsted parks. This is consistent behavior for Brown and top aide Steve Casey. Lately they have been squeezing housing and human service agencies for patronage jobs by holding back funds—or, in some cases, simply squeezing them out of existence in favor of politically friendly but shaky substitutes. And you wonder why people hate politicians.

A recently re-elected mayor with campaign favors to repay is no doubt salivating about the parks coming under his control. The bounty of parks jobs includes 150 full-or part-time positions run by the conservancy. Brown no doubt wants to get his hands on at least some of them.

Somebody needs to remind the mayor: We pay him to do what is best for us, not what is best for him.

Brown is making distracting noises about the conservancy’s diversity, wage scale and—drumroll, please—residency. Please. As far as smoke screens go, this one is as transparent as a storefront window. The city cares little about residency— it has not had a residency officer in years—and less about the living-wage law that Brown historically has contorted himself to dodge. The way I see it, this is about patronage jobs and payback to political supporters, not about what is best for our parks.

Brown has had plenty of time to figure this out. The county told him 19 months ago that it was giving back the parks. He could have cut a half-dozen deals during that time—if he really wanted to. A year ago, Brown told The News that he would fund the Olmsteds “at the present level.” What happened?

Paying the conservancy to run the Olmsteds gives the city a half-price deal on its premier parks. It is too bad we have a cut-rate mayor.