Q: AC blows cold until engine warms up.

You do not mention what kind of vehicle you have, but I can tell you that if they only put in .81 lb of refrigerant then your system is likely low on refrigerant. Most systems take more than 1.5 lb of refrigerant. If you are just using your A/C after not using it during winter time then you may have leaked some refrigerant out.

You should have the A/C system checked to see if it is running at the correct pressures when the vehicle is warm. Depending on the vehicle and outside temperatures, your pressures should be about 30 on the low side and 200 on the high side. These pressures are not exact, and will vary, but would give indication of problems if your pressures at idle are way off from these pressures. I’d recommend having the system checked by a qualified mechanic, they will be able to perform these tests and accurately diagnose your A/C issue. Once that is done, the necessary repairs can be made.