Fall HVAC checklist for Phoenix homes

By October, your AC has run hard since spring. Your heater, on the other hand, hasn't done a thing since last winter.

Fall is the one quiet stretch in a Phoenix year. The worst heat is over and the cold nights haven't started. That makes it the best time to look after both sides of your system.

Here's a checklist you can work through yourself, plus the parts that are worth a pro's eyes.

What you can check this weekend

None of these steps needs tools. Together they take less time than a trip to the hardware store.

Swap the filter

A summer of dust, monsoon storms and nonstop running is hard on a filter. Pull yours out and hold it to the light. If you can't see through it, replace it.

Write the size down while you're there, since it's printed on the frame. If dust comes back fast after you clean, our post on air quality during haboobs covers better filters.

Test the heat before you need it

Pick a mild afternoon. Switch the thermostat to heat and set it a few degrees above the room temperature.

Within a few minutes you should feel warm air at the vents. If you get nothing, or only cool air, you've found a problem on a warm day instead of a cold night.

Expect a dusty smell on that first run. Dust settles on the heater all summer and burns off. It should fade within the hour.

Clear around the outdoor unit

If you have a heat pump, that outdoor unit heats your house in winter. Pull back plants, leaves and anything stacked against it so air can flow.

Check the condensate drain

Your AC pulled a lot of water out of the air during monsoon season. That water leaves through a small drain pipe, often near the outdoor unit or into a drain inside.

Standing water by the indoor unit or a stain on the ceiling under an attic unit means the line may be clogged. Left alone over winter, a clog can grow mold and back up next summer.

Set a winter schedule

Winter days here are often mild while the nights get cold. A schedule that warms the house in the morning and evening, and eases off while you're out, keeps the bill down.

If your thermostat can't run a schedule, a smart one can. Our post on smart thermostats explains how they work.

Change the thermostat batteries

Many thermostats run on batteries and only warn you when they're nearly dead. A blank screen on a cold morning is an easy fix you can skip.

Test your carbon monoxide alarm

If you heat with gas, a working CO alarm near the bedrooms matters most in winter. Press the test button, and replace the batteries if it's been a while.

What a fall tune-up covers

Some checks need gauges, meters and a look inside the cabinet. That's where a tune-up comes in.

A spring visit gets the cooling ready for summer. If you run the heat in winter, a fall visit does the same for heating. Our HVAC maintenance page walks through the visit step by step.

On a gas furnace

• The igniter and the flame sensor, the two parts that fail most after months off
• The burners, checked for a steady flame
• The blower motor and belt
• A check for cracks that could leak carbon monoxide

On a heat pump

• The valve that switches it from cooling to heating
• The defrost controls, which clear frost on cold mornings
• The backup heat strips
• The refrigerant level, since a heat pump needs the right charge in both seasons

A heat pump runs in summer and winter, so it wears faster than an AC that rests half the year. Twice a year is the right pace for one here.

Signs it's time to call now

Some problems shouldn't wait for a tune-up. If you notice any of these during your checks, call us.

• The heat won't come on at all, or the air stays cool
• The furnace clicks but never lights
• A burning smell that lasts more than an hour, or smells like hot plastic
• Ice that stays on the outdoor unit of a heat pump
• The breaker trips when the heat starts

If you ever smell gas, skip the checklist. Leave the house and call your gas company from outside.

Most calls get a same-day visit, and there's no emergency fee. Our heating repair page explains how a visit goes. We also have pages for Phoenix, Glendale, Gilbert and Tempe.

Coming back for the winter

If you spent the summer up north, your system sat with the house closed up. Run through this list the week you get back. Our snowbird guide covers getting the house ready before you leave.