The light bulbs on the Volvo S40's dash illuminate all of the gauges and dials on the instrument panel and are an important safety feature. There are 28 bulbs on the instrument panel, and all of them will wear out over time. If you are replacing one bulb, it is wise to go ahead and replace all of them so that you will not have to remove the instrument cluster for a while. The Volvo S40's dash lights use #30618412 bulbs, which you can buy at your Volvo dealer.
Open the S40's bonnet and disconnect the battery by removing the negative cable with a wrench.
Remove the two screws from behind the steering wheel with a Phillips screwdriver and lower the steering wheel.
Remove the two screws securing the plastic around the instrument panel and pull the plastic off.
Remove the three screws securing the instrument panel and pull the instrument panel towards you. Disconnect the three connector cables behind the instrument panel by pulling them off. Pull the instrument panel out of the vehicle.
Remove the single support screw near the top of the instrument panel and press in the seven clips around the edge of the instrument panel to release them. Pull the glass off the instrument panel in order to access the bulbs.
Pull out any old bulbs and replace them with new bulbs. Reinstall the glass and secure it with the single screw and seven clips. Reattach all three connector cables and place the instrument panel back into the vehicle.
Reinstall the three screws securing the instrument panel. Reattach the plastic around the instrument panel and reinstall its two screws.
Raise the steering wheel and reattach the two screws behind it. Reconnect the battery.