If your home isn't as toasty as you'd like this winter, perhaps a heating system tune-up is in order.

No furnace will continue to operate efficiently without regular periodic maintenance. Keeping the home's heating system clean, lubricated, properly adjusted, and replacing the filter regularly will not only result in more efficient heating, but will also extend the life of the system and save energy and expense.

Ideally, the furnace should be inspected and serviced by a professional heating contractor or qualified service technician at least once a year, preferably before each heating season begins. Many heating companies offer such a service at a reasonable price. If you do your own maintenance, a qualified professional should examine the system every three to five years.

The first step in furnace maintenance is to replace the dirty furnace filter with a clean one. The purpose of the filter on a forced-air furnace is to keep dust, soot, and other contaminants out of the air that is blown into your living area. Once the filter has been sufficiently coated with this grime, it causes the furnace blower to work harder, making it more costly to operate and shortening its life span.

Since filter size and location vary from furnace to furnace, you'll need to check the owners handbook for this type of information. If an owners handbook doesn't exist, this information usually can be found on the furnace or on an inside panel of the furnace. Some furnaces have more than one filter that will need replacement one near the blower and one at each cold air return. Buying replacement filters by the case will cut down on the unit price and will make replacement convenient.

The blower compartment of forced-air furnaces should be clean and dust-free. Use a vacuum with a dust brush attachment to remove any lint, dust, or debris that may exist. The same should be done for the fire box or burner compartment. Caution: Make sure that the furnace is turned off and has had a chance to cool completely before attempting to clean it.

There is nothing more disturbing than a furnace that sounds like an automobile skidding out of control each time the blower engages. If such is the case in your home, chances are that the fan belt needs to be replaced or tightened slightly. The fan belt should typically "give" only about 1/2 inch. In most cases moving the motor bracket will usually be all that's required.

Any other squeaks and creaks can be silenced with a little lubrication. All bearings and other moving parts should be lubricated with fine machine oil. If the furnace is oil-fired, the bearings in the pump motor should also be oiled periodically. The fuel filter in the main oil line should be replaced once a year.

Finally, the burners should be adjusted to ensure that they mix the proper amount of fuel and air for safe and efficient combustion. This is something that most utility companies will do free as a service for their customers.

Q. Four years ago, I had a new 20-year fiberglass shingle roof installed on my home. The roofer that installed it went out of business two years ago (telephone disconnected and mail returned). The workmanship was warranted for only three years, but the shingles are supposed to be good for 20 years. Some of them are already beginning to show wear.

How does one deal with "warranties" by contractors who simply disappear? Who will fulfill the warranty for the "20-year shingles" if the contractor is gone? Of course, I have no record of or idea who the warranting manufacturer is. Gernot R., San Francisco, CA.

A. According to the National Roofing Contractors Association (NRCA), a leading trade association pledged to professionalism, the best way to protect your warranty is by doing your homework up front when selecting a roofing contractor to be sure that you will be dealing with a real pro. While this doesn't guarantee that all will go well, the odds will most certainly be in your favor.

Unfortunately, it appears that the contractor that installed your roof was just one of many who claim to be professional roofers, when, in reality, they have no established place of business, telephone, technical experience or credibility.

Whereas the workmanship part of your warranty has expired, you are still entitled to the material warranty if you can determine who the manufacturer of the product is and that it was installed properly. We have often seen material warranties voided due to faulty installations.

We would advise you to enlist the services of a professional roofing contractor or an experienced roofing consultant to verify the manufacturer of your particular fiberglass shingle. Once identified, the expert will likely be able to put you in touch with the manufacturer's representative who can offer some assistance.

The NRCA says that it's a good idea when reroofing to keep an extra bundle of shingles with the wrapper attached identifying the brand name and the manufacturer. In addition to providing exact identification in case a warranty question arises, it also provides replacement shingles.

A free list of professional roofing contractors located in your ZIP CODE area is available to you, along with a booklet of roof care tips, by sending a self-addressed stamped envelope to the NRCA, Buying a New Roof, 10255 W. Higgins Road, Suite 600, Rosemont, IL. 60018, Attn: Lillian