Rebuilding a cooling unit is more than simply repairing the specific cause of its failure. Rebuilding is also doing what it takes to increase the likelihood of a long life for the cooling unit. Below is the process by which over 90% of our cooling units are rebuilt.

Cooling unit cores are inspected for failure causes, then the solution inside is discharged and the cooling unit is thoroughly flushed and cleaned.
Although not every cooling unit has rusted out evaporator coils (the "head"), there is always some deterioration and the majority of them do need re-tubing. New heads, which are a pipe inside of another, are manufactured and stored for later use. No patch work.
Since replacing the head is fairly major "surgery", a jig is required during the welding stage to insure that all parts of the cooling unit line up where they're supposed to.
After welding, the units are tested for leaks and charged with an ammonia solution, then pressurized with hydrogen. Once charged, the units are bench tested for operation and more leak tests.
The units are then painted
New polyurethane foam is foamed back onto the heads.
Insulation packs are installed on the units, and they are ready for shipment.