A whole house fan is a great alternative to air conditioning in helping to cool your home; however, when an old whole house fan ceases to function you'll need to repair or restore it. Generally speaking, your whole house fan is much like any other type of common household electric fan and is fairly simple in its design and there are only so many things that can go wrong with a whole house fan.
Common Whole House Fan Problems
The most common problem that causes whole house fans to cease functioning is a burnout or defective motor. You can use a circuit tester or multi-meter to check to see if the motor is faulty. If the motor is found to be faulty, it is usually a lot cheaper and easier simply to replace the motor. In many whole house fan motors, the manufacturer uses a thermal fuse to help protect the motor from overheating. The fuses are usually in-line fuses and are not as simple to replace as some types. However, you can purchase in-line fuses at RadioShack and other electrical supply stores, and replace them yourself.
Another problem common to variable speed fans is a faulty switch. If you suspect you a faulty variable speed switch, try wiring the fan directly to the plug-in cord to see if the fan functions. If you need to replace the switch, you can purchase a variable speed switch it at many home improvement stores.