Did it start immediately after the new AC compressor and evaporator was installed, or some time later?
If immediately after it could be that they used some kind of silicone sealant during the assembly, and would fade away soon.
If you use it constantly in re-circulation mode it's prone to grow fungus/algae.
If immediately after it could be that they used some kind of silicone sealant during the assembly, and would fade away soon.
If you use it constantly in re-circulation mode it's prone to grow fungus/algae.