Repair a Construct

Repairing a construct or vehicle requires both parts and tools. In addition, some repairs will require a hangar, dry dock or a garage. The GM has the final say about what is actually required to be able to attempt repairs on a vehicle.
Repairing a construct takes time. As per the sidebar on page 222 of the Genesys Core Rulebook, repairing a ship takes between days for light damage and up to months from for highly damaged vehicle.
While this works well for a story in which your GM wants to player characters to stay in a location for a prolonged time as the hangar’s staff is doing the repairs, you might want to allow a character to work faster when they are doing it on their own, as having a character repairing a vehicle for a month can slow down the adventure’s pace. Therefore, this author recommends that for each full day of work on the vehicle, make a Mechanics check determining the outcome of the repairs.
Repairing a vehicle is different than the Damage Control your character may attempt mid encounter. If anything, repairing a vehicle when there is no immediate threat is more akin to Medicine checks.
Table III.2-16: Damage Control Article on page 228 of the Genesys Core Rulebook gives the difficulty to attempt repairs as per the current level of Hull Trauma of the vehicle.
Repairing Critical hits
If the character is specifically trying to repair a Critical Hit to the vehicle rather than Hull Trauma, the difficulty is the severity of the Critical Hit. Depending on the situation, the GM might require that parts are required to attempt such repairs. In this case, this author recommends that the parts should be worth about 50 times the Critical Hit’s severity. Finally, this author suggests that you multiply that cost per the Price Modifier Table Vehicle Silhouettes and Suggested Characteristics on page 60 of the Genesys Expanded Player's Guide. A simplifed version of this table is displayed here:

Silhouette	Price Modifier	Motorcycles
1	x0.5	Drones, Wagons, Smallest Ironclads
2	x1	Carriages, Small Fishing Boats, Small Ironclads
3	x1	Skiffs, Single Train Cars, Gliders, Large Ironclads
4	x1	Trains, Single-Masted Ships, Zepplins
5	x2	Three-Masted Ships, War Zepplins, Collosal Ironclads
6	x10	Five-Masted Ships, Heavy Freighters
7-8	x100	Small Open Water Stations
9-10	x100	Large Open Water Stations

When making this kind of repair, no Hull Trauma can be repaired on that check.
EXAMPLE #1 OF A REPAIR A VEHICLE CHECK
Fivel is a student mechanic, working part time at the nearby drydock, when not adventuring with his friends. Being relatively poor, Fivel cannot afford to buy a nice skiff to sail the shores himself. Yet, he found a deal when buying an old broken sailing skiff from a scrapyard. The vehicle currently exceeds its Hull Trauma Threshold and suffers from the Brakes Damaged (ddd) Critical Injury.
Each time he earns money, he buys parts to repair his ride. He recently invested $250 worth of spare components. His first goal is the get the engine to start and repair the frame, which is represented by the fact that the vehicle's Hull Trauma is above its threshold.
The Difficulty of such check, as per the Table III.2— 16 on page 228 of the Genesys Core Rulebook, is Hard (ddd). Fivel works on the skiff in his drydock's old storage shed, using whatever tools he can borrow or scavange. The GM adds b to the check, which Jeff negates through his Knack for it (Mechanics) Talent (see page 73 of the Genesys Core Rulebook).
The check generates sssh. The repairs to the chassis removed 2 Hull Trauma since he generated 2 additional s. These repair cost him 100 silver worth of parts. The GM spends the h to have the skiff suffer 1 system strain. Crude repairs made with poor tools, the silverline sails suffered a bit, which Fivel will take care of later. The good news is that these repairs were good enough to lower the vehicle's Hull Trauma one point below its threshold. Therefore, the skiff is functional... despite the fact that the brakes are not working. After all this work, Fivel calls it a day.
On the next day, Fivel attempts to repairs the brakes, spending 150 silver. Due to the Critical Hit's severity, the check is Hard (ddd). The check generates aa. Since the check failed, the brakes are not repaired yet the parts are spent. Fivel's player spends the aa to reduce the vehicle's System Strain by 2 points. Out of silver after these two attempts, he will have to wait for his next salary to pursue further repairs on the skiff.
EXAMPLE #2 OF A REPAIR A VEHICLE CHECK
The Perriwinkle is a merchant freighter carrying goods from the Tribute River Delta to the city of Rystanburg further up the shore. On its last journey, it was attacked by murloc, suffering heavy damage. The GM tells the PCs that the damage on their ship can only be repaired in dry dock. Fortunately, the vessel's sponsoring company has their own and the player characters can make repairs themselves.
The ship's current Hull Trauma value is just above half its threshold. Therefore, the difficulty is Average (dd). Due to their proper installations, Buck, the character making the check, adds a b to the pool. While the crew takes some days off, the other PCs, who also feel a debt to the ship's captain, assist Buck with the repairs. Together, they add bbb to the skill check. The GM spends a story point to upgrade the difficulty of the check, narrating this as someone from a rival company is trying to take advantage of the Perriwinkle's situation to sabotage it, giving them an advantageous position for getting the best trade deals on the tributary trade route.
The check generates ssad. Since the check is successful, the PCs repair 1 Hull Trauma. They did not generate enough additional s to repair an additional Hull Trauma that day. The a is spent to reduce the ship's System Strain by 1. The GM spends the d to have the saboteur break the ship's main mast, inflicting the Propulsion Damaged (dd) Critical Hit, dropping the ship's Speed value from 3 to 0.
The following day, Buck will attempt to make the repairs again, but will do so alone as the rest of the PCs will be investigating who sabotaged their ship. Buck spends the 200 worth of silver (50 per severity level, multiply by 2 for being a silhouette 5 ship) for acquiring parts to repair the mast. Making an Average (dd) Mechanics check, he generates sat. The successful check allows him to repair the mast while the a and the t are spent to reduce the repairs cost, as the crew was on tight budget. These symbols will reduce the cost of parts from 200 to 120 (200-10% from the a and -30% from the t). The leftover parts, worth 80 silver, will be kept on the ship for future repairs.