Nasa had grown anxious about the altitude control thrusters on Voyager 1, which have been wearing down.
The set of four small thrusters came online Wednesday after NASA engineers noticed the spacecraft's attitude control thrusters had been degrading for several years.
While the ACMs work, since 2014 they've use more fuel than in the past.
Artist's concept of the Voyager 1 spacecraft. Those thrusters aren't functioning well anymore, so NASA engineers figured out how to revive a different set of thrusters called "trajectory correction maneuver" (TCM) thrusters. As the TCMs are mounted on the craft's rear and Voyager doesn't need a speed boost - it's already doing 17.46 km/hour - they've been left alone since 1980.
Todd Barber from JPL also said: "The Voyager team got more excited each time with each milestone in the thruster test".
"On Tuesday, Nov. 28, 2017, Voyager engineers fired up the four TCM thrusters for the first time in 37 years and tested their ability to orient the spacecraft using 10-millisecond pulses", NASA said in a statement. According to Voyager project manager Suzanne Dodd, the reactivated thrusters should help extend the life of the probe for another "two to three years". She added that the Voyager team is so chuffed with the result, they may test the TCMs on Voyager 2, too, even though its ACMs continued to perform well.
Engineers say the back-up thrusters - more used to being fired continuously - worked just as well in short bursts to reorient the spacecraft towards Earth.
They wanted to reposition Voyager 1, which, at 21 billion kilometres away is the space agency's most far-flung spaceship. Data still flows from Voyager to Earth, though it takes around 19 hours to make the trip.
All of Voyager's thrusters were developed by Aerojet Rocketdyne. And, it seems Voyager's still got a few tricks up its sleeve.
Controllers at JPL plan to switch to the TCM thrusters full-time in January, giving Voyager 1's other rocket jets a rest. To make the change, Voyager has to turn on one heater per thruster, which requires power - a limited resource for the aging mission. It was a message from Voyager 1, the only man-made object in interstellar space.
NASA will likely do a similar test of Voyager 2's TCM thrusters, which could be used if that spacecraft's attitude control thrusters further degrade in the future. The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in Washington.