Central A/C turned on last night and within 5 minutes the entire house smelled like smoke - the kind of smoke that comes from an electrical fire. I immediately turned the system off and checked the unit. Found nothing amiss with the compressor/condenser outside the house. Checked the indoor component that sits atop the furnace in the basement and found nothing wrong or on fire. Incidentally, loud clicking sounds were coming from the furnace right before the smell of smoke was noticed.

This is the first time this happened. The A/C unit is only 2 years old and the furnace is about 6 years old.

Any help or advice would be appreciated!