How to Troubleshoot a Whole-House Fan. By pulling in cooler air, a whole-house fan reduces or eliminates the need for air conditioning. Best of all, whole-house fans use only one-tenth of the energy that air conditioning does. But when the fan isn't working the way it should, follow these steps to troubleshoot the problem.
Check that a whole-house fan is receiving electrical power when it doesn't work at all. Look at the circuit breaker or fuse box to see if a switch has flipped. If this doesn't fix the problem, a burned-out fan motor may need replacing. Other possibilities include damage to the wiring or a switch, best repaired by an electrician.
Replace a loose or broken belt in the fan motor if your whole-house fan runs, but doesn't produce any airflow.
Ensure that your fan can run at higher settings by checking the exhaust ventilation. You should see intake vents in the overhang or just below. Make sure the exhaust vents lie near the ridge of the roof.
Stop fan humming by using the anti-hum feature if it's available. An annoying hum is a common complaint with whole-house fans. Generally, the more blades you have, the quieter the fan runs. Less expensive models often have fewer blades and no anti-hum feature. In this case, running the fan on low can reduce or eliminate humming.
Open windows if the shutter rattles. More air helps the shutters open all the way. Usually the heavier the fan and louvers, the less of a problem this will be. Make sure there is at least 30 inches of clearance above the blades of the fan, or air will be forced back through the shutter.
Eliminate damp smells from the fan by checking your attic for leaks. If you can't find any leaks, but the humidity seems high in the attic, look for improper venting.
Understand that, with a whole house fan, it's normal for attics to be 20 degrees hotter than the outside temperature. Higher temperatures can result from darker shingles as well.