Cooler air is now circulating in the Farragut North and Dupont Circle stations after more than four years of problems with the cooling system.

The temperatures in the stations reached into the mid-to-high 90s on the hottest days this summer, frustrating sweaty customers. Metro used fans to cool the stations, but it did little to fix the heat.

All of Metro’s underground stations are cooled by systems that move cold water to air handling units. As the water passes through the air handling cooling coils, chilled air is produced for the stations, lowering the temperature about six degrees from the outside temperature.

The original pipes under Connecticut Avenue were damaged or deteriorated, meaning cool air hadn’t been circulated to the stations since 2015. Metro tried to fix it with minimally-invasive solutions, like pumping sealant through the piping, but that didn’t work, so all the pipes had to be replaced.

This week, crews finished work and testing before restarting the chillers, which are now pumping cooler air into the stations.

“Metro thanks our customers for their patience while unanticipated delays impacted this project,” the transit agency said in a release.

Metro used a temporary fix during two summers that put big cooling equipment on Connecticut Avenue. The transit agency didn’t have that option this year because it thought the permanent work would be done.

A permanent fix was supposed to be in place by May, but Metro announced several more delays in June and August. An unexpected light pole that wasn’t reflected in engineering drawings caused one construction delay, as crews had to get permission from the city to move it out of the way.

Metro announced earlier this month that contractors finished the pipework, but found leaks within the chiller plant itself.

Meanwhile, riders sweltered in the stations. But the cool air may not be as needed now, as humidity has started to dissipate and fall approaches. Temperatures will be in low 80s to low 90s this upcoming week.

Several other stations, including Union Station and Virginia Square, also had chiller problems this summer.

This story originally appeared at WAMU.