Unexplained Cold Spots
Should you suddenly notice cold spots, it's likely that your ducts need cleaning. Uneven heating could also indicate that it's time to change your filter or clean the blower.
Furnace Cycles Are More Frequent
If a furnace needs cleaning, it's going to be working harder to heat your home. In order to compensate for the extra effort, your furnace may kick in more frequently. This may also result in higher than expected utility bills from the extra operating time.
Increase In Allergy Symptoms
A furnace or HVAC system does more than keep your home comfortable. If filters are clogged, you may notice an increase in allergy symptoms or respiratory issues due to dust or allergens re-circulating through the air.
Added Noise During Operation
Some heating systems will become louder than usual when certain parts have to work harder to heat your home. For instance, the blower may suddenly produce more noise as it tries to force air through a dirty or clogged furnace or heating system filter.
Some basic furnace maintenance is a do-it-yourself job and other tasks are best performed by professionals. As a general rule, a furnace should be cleaned and inspected at least once a year to make sure everything is working as expected. This is especially true if you have an HVAC system that's heating and cooling your home in Myrtle Beach year round.
HVAC Maintenance Checklist, HouseLogic
Maintenance Checklist, EnergyStar.gov