Weathervane (quest)

Weathervane is a Railroad radiant quest in Fallout 4. It belongs to a chain of semi-random quests provided by Tinker Tom in the Railroad HQ. He thinks the Institute is trying to "terraform" the Commonwealth by poisoning the atmosphere, so he designed atmospheric sensors called MILA to detect any anomalies in the air. He asks the Sole Survivor to help place these devices on high vantage points throughout the city. The number of locations is fixed, but the order in which they are given is random.

Quick walkthrough

 * 1) Report to Tinker Tom.
 * 2) Plant MILA device.
 * 3) Report back to Tinker Tom.

Back Street Apparel
This location is defended by a group of raiders and two turrets, one outside on the flatbed truck and the other inside on the ground floor. Enter the building to gain access to the rooftop where the MILA drop-off location is. Once the MILA has been planted, return to Tinker Tom for a reward and a new assignment.

Boston Bugle building
The entrance is through one small door on the side of the building. Take the elevator at the back of the first room you enter. After exiting the elevator you will see a door directly to your right. There is a protectron in the room you exit into. Take this to the roof of the Boston Bugle where you will find the area to place the MILA and return to Tinker Tom for a reward and a new assignment.

Broken monorail
To reach your location, you must first go inside the Haymarket Mall and fight your way through both raiders and a few turrets. Keep on climbing up until you reach the roof. Beware, once you exit into the roof, a deathclaw will be waiting for you. Once the deathclaw is killed, look around the building until you see a monorail train hanging underneath the highway. In order to enter the train, simply follow the catwalk down. Carefully walk across the monorail train until you reach the end (sometimes, a protectron will spawn and be hostile towards you). There you should see a plank where you place your MILA. Once this is done, return to Tinker Tom for a reward and a new assignment. Note: If you have already gone through this location to the roof, you can fast travel directly to Garden Terrace, where you will meet the deathclaw. Or alternatively, you can directly access the monorail roof via the elevated roadway by climbing through the ruined building to the south west of Faneuil Hall which avoids having to fight through the raiders or the deathclaw. There is a gap in the road above the terrace building roof, from which you can drop directly onto the monorail.

Cambridge construction site
The site is partially walled off and infested by super mutants. Head inside and use the staircase to climb the building while fighting off the enemies. At the top of the structure there is a small shack walled area with a red loot chest and a random leveled super mutant in it. Kill him and place the MILA on the vantage point extending from a I-beam. Return to Tinker Tom for a reward and a new location.

Camp Kendall
This location is defended by a group of raiders, some of which can be found on rooftops. Walk up makeshift ramps towards a button to call a lift that can be used to access the rooftop where the MILA drop-off is. Once the MILA has been placed return to Tinker Tom for a reward and a new assignment.

Commonwealth Bank
The front of the bank is defended by a small group of raiders and a single turret. Once these are taken care of, the vantage point is accessed by using the elevator by the entrance. Exit the elevator and enter another elevator to the roof of the bank, where one can place the MILA. Once this is done, return to Tinker Tom for a reward and a new assignment. Or alternatively, you can directly access the forth floor via the a door and walkway on the west side linked to the elevated roadway, by climbing through the ruined building to the south west of Faneuil Hall. This avoids the locked door, raiders and turret.

Corvega assembly plant
The plant is heavily guarded in- and outside by raiders. Head around the back and climb up the structure next to the plant while fighting off raiders. Walk along the sky bridge and onto the plant. Continue fighting off raiders while going up and along the catwalks and at the far end of the catwalk next to the large sphere will be the MILA vantage point, next to which is the repair bobblehead. Return to Tinker Tom for a reward and a new location.

Four Leaf fishpacking plant
The plant is defended by a group of feral ghouls, and possibly a pack of super mutants in the building to the east. There is an external staircase on the southern corner of the plant for easy access to the rooftop where the MILA can be placed at the northernmost point of the roof. Once the MILA has been placed return to Tinker Tom for a reward and a new assignment.

Hub 360
This location is defended by super mutants, to gain access to the rooftop where the MILA drop-off is take the lift that is located on the Fallen Skybridge, which can be accessed via a staircase south of Goodneighbor. Once inside Hub 360 enter the lift and travel up to the rooftop, place the MILA and then return to Tinker Tom for a reward and a new assignment.

Mass Bay Medical Center
The medical center is defended by Gunners and a single assaultron. There may also be a set of power armor inside the medical center which can be utilized by the Gunner. Enter the medical center and travel up two elevators to gain access to the rooftop where the MILA drop-off location is. Once the MILA has been placed return to Tinker Tom for a reward and a new assignment.

Parkview Apartments
The location is on the top of the building, there are raiders and super mutants battling on top of the apartments. Enter the apartments, climb the stairs and the use the elevators to get to the top. Place the MILA on the vantage point and return to Tinker Tom for a reward and a new location.

Bugs

 * If you eliminate the Railroad for the Institute or the Brotherhood of Steel and kill Tinker Tom, you will not fail this quest. It will remain an active quest and direct you to turn it in to Tom's corpse. It is also possible that you will fail one instance of this quest but immediately get another MILA and another quest target to place it (with no possibility to finish).
 * One can use the console command to fix this.
 * The number of locations can be fewer than 11 if one or more of locations have already been cleaned before. It is not known for sure if this a bug or it was conceived by developers. If one wants to complete all 11 locations despite this, one can use the console command to add the next quest in the chain.
 * The door to the Boston Bugle may not be highlighted, while tracking the mission. (It may be that the highlighted door is up high rather than the ground floor door.)
 * Having a MILA in your inventory may not be necessary to activate a vantage point. Occasionally, the player will get a "turn in to Tinker Tom" message, though the device does not appear.