Unfortunately, bad coolant hoses will not cause the AC to blow warm air. But if a coolant hose is leaking it can cause many other issues. To clear up the issue with the warm air coming out of the vents when the AC is on, You should really have the HVAC system checked. The most common problems that we find are leaks in the system. Once the refrigerant gets low it will prevent the compressor from turning on. Best of luck to you and i have given you a link for some local shops that will be able to help you.