Caution: Please read our safety information before attempting any testing or repairs.
Before replacing any of the fans, unplug the PC to avoid an electrical shock hazard. Exercise caution as there are sharp edges on a PC and its components. Always wear a static electricity discharge strap when working with your PC's components to avoid damaging your PC.
Your PC probably has two or more fans. Common fans include a power supply fan, CPU fan, case fan and drive fan. Each of these is generally replaceable with the exception of the power supply fan. Some power supplies have replaceable fans, but many do not. If the fan is not replaceable, then you will have to replace the power supply.
Note: Cleaning your existing fan may solve your problem. The build up of dust and grime may slow or stop an otherwise working fan.
Case Fans
Case fans can be mounted to the case, in a drive bay or installed in a slot. They are easy to remove and install. If replacing a fan, simply open the case, locate the fan, disconnect it from its power source, remove any fasteners holding the fan in place and install the new fan. If you are installing a new fan, rather than replacing one, then locate a suitable position for the fan, secure the fan in place, connect it to a power source (typically one of the power connectors from the power supply or possibly a connector on the motherboard designated for powering a case fan.
Drive Fans
Drive fans typically mount in an available drive bay and connect to a power lead from the power supply. Whether installing a new fan or replacing an existing fan, open the case, locate a bay that will best move air over the drives. Secure the drive fan into the drive bay and connect it to the power supply.
Power Supply Fan
If the fan in the power supply does not spin, spins slowly or makes excessive noise, then it must be replaced. Upon inspection of the power supply you should be able to determine if the fan can be replaced. If you find no screws securing the fan and the unit appears to be held together with rivets, then you will probably have to replace the entire power supply. Do not try to replace the fan if it is not designed to be replaced. Note that the power supply may contain a capacitor holding a potentially dangerous electric charge, even when unplugged. Use caution when opening the power supply, do no touch interior components unless you discharge the capacitor first. To replace a modular a fan, remove the screws securing it in place, disconnect the power connector and remove the fan. Connect the new fan and secure it in place.
CPU Fan
CPU fans may mount to the CPU and socket on the motherboard, may fasten to a fan mount or fasten to the case and channel air flow to the CPU with a shroud. Replacement of the case or specialized fan is fairly easy. Disconnect the power connector, remove the screws or clips securing the fan in place and install the new fan.
CPU fans that mount directly to the CPU can be trickier to install. Use of excessive force, slippage of tools, misalignment of fan can result in damage to the CPU, motherboard or both. First of all, avoid touching the bottom of heat sink attached to the fan. Skin oil and dirt will reduce the effectiveness of the fan and heat sink. Clean the bottom of the heat sink with an alcohol swab and let it dry before installation. Apply a small amount of thermal grease to the bottom of the heat sink and spread it with a gloved fingertip. Orient the fan so that the spring latch aligns with the tabs on the CPU socket (note the small tabs on the left and right side of the socket in the photo below)
Align the heat sink so that the smaller side of the spring latch aligns with one of the tabs on the CPU socket. Now check that the power connector can reach the CPU power connector on the motherboard. Now lower the spring latch and hook it under the tab on the socket. Set the heat sink/fan unto the CPU and carefully pull the spring latch down to hook onto the tab on the other side of the socket. If you use a tool, such as a screwdriver, to push the latch down, you risk it slipping off and damaging the motherboard. If you have difficulty, try using the eraser end of a pencil to push on the part of the latch inside the fan housing while pulling the spring latch with you other hand. It can be challenging; take your time or you may destroy the CPU or motherboard.