Pick your number.We keep it there.

The AC is blowing warm air.

It usually comes down to one of these:

• A clogged filter starving the coil of air
• A failed capacitor or contactor at the outdoor unit
• A refrigerant leak

Check first: thermostat on Cool, breaker on, filter clean.

The heat won't come on.

It usually comes down to one of these:

• The thermostat or a tripped breaker
• A failed igniter or dirty flame sensor
• A heat pump stuck in the wrong mode

Check first: thermostat on Heat, breaker on, furnace switch on.

One room never feels right.

The system can be fine and the air still not get there:

• A leaking or disconnected duct
• Crushed duct or too little return air
• A system that was never balanced for the house

Check first: is the vent in that room open and clear?

There's water or ice at the unit.

It usually comes down to one of these:

• A clogged condensate drain line
• A frozen coil, from weak airflow or low refrigerant
• A cracked drain pan

Do this first: turn the system off so the water stops.

It started making a new noise.

The sound is usually a clue:

• Banging or rattling: a loose part or failing blower
• Squealing: the motor or a belt
• Hissing: a duct or refrigerant leak

If it's loud or it smells like burning, turn it off.

It's old and the bills keep climbing.

Three signs it's time to talk about a new system:

• A worn compressor or motor losing efficiency
• A system sized wrong for the house
• An older unit on R-22, a refrigerant no longer produced