This is common for most 240's. The airconditioners can be wimpy and troublesome. Additionally, make sure the AC drain that remove condensate from the coils is clean and draining properly or it will pool under the front floormats causing rust. Check under the front floormats for dampness. When ACs are working properly they are OK but nothing to write home about.
Later models are more up to the task.
Make sure the scheduled maintenance has been performed. Especially the timing belt replaced, fluids regularly changed, etc. Most Volvo owners are more than proud to show you their service records. Be extremely cautious or avoid used Volvos that dont include their full maintenance history. Always have a prospective car checked by a private, independent mechanic. who exclusively services Volvos.