For a fan to perform efficiently it is very important that the blade be flat throughout. Most manufacturers have programmes to investigate keeping warpage to a minimum. "Balanced" blades; that is, blades that are electronically matched at the factory; are sold as a balanced set, depending on the design of the fan. For this reason, never interchange blades between fans.

There are several reasons why a ceiling fan wobbles. The blades could be out of balance, out of track, or warped. The wobble could also result from air turbulence caused by the blades being closer than six inches from one side of a sloped ceiling or ceiling beam.

n You can check to see if the fan blades are out of balance by clipping a spring-type clothes pin to halfway between the tip and the blade iron on the leading edge of one blade. Turn the fan on to a low speed and see if the added weight stops the wobble. Try each blade to determine if it needs more weight. If the clothes pin stops the wobble, contact your fan manufacturer's servicing center to correct the fault.

n Check to see if one or more of the blades are out of track. Using a yardstick, measure the distance from the ceiling to the tip of each blade -- it should be equal for each blade. If the distances vary, contact the nearest manufacturer's service centre about correction or warranty replacement. If the blades are not out of track, try swapping the blades to correct the problem. Switch the position of two blades, while leaving the other in its original positions. While the blades are off the fan, lay them on a flat surface to see if they are warped; if so, replace them.

n Be sure all blades are screwed firmly into the blade holder. All blade holders should be tightly secured to the fan. Wobbling may be checked by using a household yardstick. Place the yardstick vertically against the end with the outside leading edge of a blade. Turn the blades slowly back to view the remaining blades. This checks alignment and tracking for bent holders. Holders should be replaced if bent.

Fans that creak or make a noise are often in need of greasing. You can do this at home. If the noise persists, there may be some technical defect. Contact the company service centre to attend to the problem.

(Compiled by Chetna Banerjee)