A refrigerant leak may develop from the AC evaporator causing the AC to blow warm air. Verifying failure of this component is difficult. A good shop will use leak detection dye to verify a failing evaporator.Google+
Car Problem Reports
Volvo C70 AC Evaporator May Leak
Volvo C70 Problem
Average Mileage: 71,333 mi (23,000 mi - 112,000 mi)
Visitor, 2007 Volvo C70, 100,000 mi
AC runs for anywhere from 2 minutes to 10 minutes and possibly longer. The hotter it is outside the shorter it runs. Then it blows swampy warm air.
Visitor, 2008 Volvo C70, 67,000 mi
2008 Volvo C70 Evaporator leak. Cost to repair ~$1000. AC recharge is only about $60, so I may let it slide for a while.
Visitor, 2008 Volvo C70, 23,000 mi
air condition is not working
Visitor, 2001 Volvo C70, 112,000 mi
The repair shop had to recharge the system to find the leak, even after the system earlier had been injected with a dye. They quoted a $1500 charge to fix. with $1,350 of the charge for labor. Have not decided wether it is worth it to fix.
Visitor, 2001 Volvo C70, 58,000 mi
Car repair conducted leak test to diagnose. Leaking evaporator was identified. $3K to replace.