The door lock assembly is one of those parts of the Volvo S70 that rarely cause problems, but when it does, it could mean a ton of headaches and costly trips to the mechanic. The following are some of the common problems of the Volvo S70 door lock assembly and their likely causes:
If the lock doesn't open and starts vibrating, this is likely due to a burnt-out actuator. Door lock actuators are small motors placed on the door panels that lock or unlock the door, and once they get burnt they must be replaced in order to use the locks again.
If the lock is making a clicking noise, it could mean a problem with the door lock actuator. However, if the lock is deactivated and is still making a constant clicking, ticking or snapping noise, the problem is more likely to be with the electrical connections rather than the actuator itself. In most cases, the ground wire may have come loose and the noise you're hearing is due to the electrical current jumping from the loose wire to a nearby metal object. In such cases, the service panel has to be removed and the loosened wires inserted back into the actuator.
A standard feature in both Volvo S70 model years, the remote power locks have been known to malfunction after 15,000 miles, and this can be due to a number of reasons. First, check the remote to see whether the battery is charged and both ends are touching the contacts. Next, open the fuse box and check if the fuses are all functional using a voltage meter. If no electricity is going through any of the fuses while the engine is running, replace them and see if the remote locks will work. If the locks still refuse to activate, the only remaining possibility is a problem with the control box, a device that receives and interprets the signal from the remote. While it is not likely that all of the wires of the control box would malfunction simultaneously, there's a good chance that the control box itself is faulty and is in need of repair or replacement.