For starters, once a year, vacuum out the area around the furnace’s blower. If possible, also slide out the fan unit, clean each fan blade with a toothbrush, and then vacuum with a brush attachment on a vacuum cleaner. While you’re at it, look for oil ports on the motor, normally located near the motor shaft. If the motor has these, apply two to three drops of non-detergent motor oil into each port (you may have to remove a cover plate to do this). Though most contemporary motors don’t require lubrication, do lubricate motors with oil ports once a year. For more about maintenance, see Maintenance Checklist for Central Heating Systems.
Yes. You should expect to pay a diagnostic fee to cover the cost of the technician's visit, the diagnosis of your air conditioner's problem, and a quote for the repair options. You will be advised of the issue along with recommended options to correct it, which may include a system replacement if your unit is old or significantly damaged. If you decide to replace the system, the diagnostic fee will be credited toward your replacement purchase.