Switching from Cooling to Heating: Your Fall HVAC Checklist

Oklahoma Fall Weather Doesn't Wait

If you've been through even one Oklahoma fall, you know the drill. It's 90 degrees on a Tuesday, and by Thursday night you're digging out a blanket. We've seen the Norman and Moore area go from running AC in the afternoon to needing heat by midnight — in the same day.

That kind of swing means your HVAC system doesn't get a clean off-season. It needs to be ready to heat with little notice. The worst time to discover a problem with your furnace or heat pump is the first night it drops into the 30s.

Here's what to do now, while you're thinking about it.

Test Your Heat Early

This is the single most important thing on this list, and it takes two minutes. While it's still warm outside, switch your thermostat to heat mode and set it a few degrees above the current indoor temperature. Let the system run for 10-15 minutes.

What you're looking for:

Warm air from the vents — It should heat up within a few minutes.
No strange smells after the first few minutes — A brief dusty or burning smell is normal if the system hasn't run in months. It should go away quickly. If it doesn't, shut it off.
No unusual noises — Banging, screeching, or repeated clicking means something needs attention.

If the system doesn't produce heat, or something seems off, you've got time to schedule a repair before the rush. Every HVAC company in Central Oklahoma gets slammed the first week of real cold weather.

Change Your Filter

Your filter worked hard all summer handling Oklahoma's dust, pollen, and cottonwood. By September, it's likely due for a change even if you've been staying on top of it. Start heating season with a fresh filter.

A clogged filter reduces airflow, makes the system work harder, and can cause a furnace to overheat and shut down on its safety limit. MERV 11-13 is what we recommend for most homes in our area — enough filtration to make a difference without restricting airflow.

Check Your Thermostat Settings

A few things to verify:

Switch from "cool" to "heat" — Sounds obvious, but if you have a manual thermostat, it's easy to forget.
Review your schedule — If you use a programmable or smart thermostat, update the schedule for fall. You probably don't need it as cold at night as you did in July.
Check the fan setting — "Auto" is correct for most situations. "On" keeps the fan running constantly, which can make the house feel drafty in heating mode.
Battery check — If your thermostat runs on batteries, replace them. A dead thermostat in the middle of the night is an unpleasant surprise.

Heat Pump Owners: Know Your System

A lot of homes in the Norman, Moore, and Purcell area have heat pumps rather than traditional furnaces. Heat pumps work great in mild weather, but there are a few things to be aware of as temperatures drop.

The reversing valve — This is the component that switches your system from cooling to heating. If you test the heat and get cool air instead, the reversing valve may be stuck or the control signal may not be reaching it. This needs professional diagnosis.
Auxiliary/emergency heat — When temperatures drop below about 30-35 degrees, most heat pumps can't keep up on their own. Your system should automatically engage backup heat strips or a gas furnace. Test this by setting the thermostat to "emergency heat" briefly to confirm it works.
Defrost cycles are normal — When it's cold and humid, your outdoor unit will periodically go into defrost mode. The outdoor fan stops, and you might see steam. This is normal — the system is melting ice off the coils.

Furnace Safety Basics

If you have a gas furnace, fall is the time to address safety:

Carbon monoxide detectors — Make sure you have working CO detectors on every level of your home, especially near bedrooms. Test them and replace batteries. If your detectors are more than 7 years old, replace them entirely.
Check venting — If you can see your furnace exhaust vent (PVC pipe going outside), make sure it's clear of debris, bird nests, or anything blocking the opening.
Look for rust or corrosion — Visible rust on the furnace, especially around the heat exchanger area, is a warning sign. A cracked heat exchanger can leak carbon monoxide.
Listen for the ignition sequence — When the furnace starts, you should hear the inducer motor, then the igniter click, then the burners light. If it tries repeatedly without lighting, shut it off and call for service.

The Full Fall Checklist

Here's everything in one place:

Test the heat for 10-15 minutes
Replace the air filter
Update thermostat schedule and settings
Test batteries in thermostat and CO detectors
Clear debris from around the outdoor unit
Check furnace exhaust vent for obstructions
Verify CO detectors are working on every level
Inspect visible ductwork for disconnections
Schedule a professional fall tune-up

A professional heating tune-up covers everything you can't check on your own — the heat exchanger, gas connections, electrical components, and safety controls. It's the best investment you can make before winter.

Call Trinity Climate Control or schedule online to get your fall tune-up on the books. We serve Norman, Moore, Purcell, Blanchard, Newcastle, Goldsby, and all of Central Oklahoma.