What is your HVAC system not doing?
How long have you had this problem?
About how old is your system?
Is your system Gas or Electric?
When was the last time your heating and cooling system had maintenance?
Do you have rooms that get too hot or cold?
Is your system loud when it is running?
Do you smell the system when the blower comes on?
Are there any funny noises, screeches, pops or thuds?
Do the lights dim when your system comes on?
KNOW Heating in Columbus Troubleshooting before you call for service in Columbus