The convertible top may have problems with the micro-switches and potentiometers that help control the raising and lowering of the top.
Knocking noises going over bumps can be caused by worn sway bar end links . These end links have small ball joints that become loose and rattle. Replacement is the only fix.
The upper engine mount may wear prematurely. Symptoms may include a harsh feeling when the transmission is shifting and roughness when the engine is idling. Worn engine mounts should be replaced as necessary.
The anti-lock brake system (ABS) warning light and/or other dash warning lights may illuminate due to a failed ABS Control Module . Replacement of the failed module is generally required to correct this concern.
Door window regulator failures have been reported. These vehicles have a very complex door window mechanism that can be very difficult to adjust properly after installing a new window regulator. This can lead to air leaks, wind noise, and a door that doesn't open or close properly. This is a good time to find an experienced Volvo mechanic !
Several complaints have been reported regarding Volvo C70 transmission shifting issues. Long shift times between gear shifts, hard shifting, hard downshifting and a loss of transmission operation all together to name a few.
If the issue is minor, a transmission software update may fix this issue so if available, the software should be updated before any repairs are made.
There are several technical service bulletins (TSB's) available from Volvo that address these shifting issues and they should be consulted by the repair shop during the automatic transmission diagnostic process.
Regular servicing of the transmission fluid can help with preventing transmission failure, but not in all cases. Follow the suggested fluid replacement interval recommended by Volvo. You will find this in your owners manual, or find it here: http://bit.ly/Volvo_Owners_Manuals
Front upper strut mounts may wear prematurely, resulting in loud noise from the front of the vehicle when going over bumps.
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.