Fall Heating Prep Checklist: 7 Steps Before First Cold Night
October is the right month to test heating. Here's the checklist so you're not calling on a 34° December morning.
Valley winters are mild but real — December and January regularly drop into the 30s at night. Furnaces and heat pumps that sat idle since April don't always start cleanly. Here's the fall checklist.
1. Test heating in October, not December
Set the thermostat to HEAT and drop it 3–5° below current room temp. Confirm warm air at the supply register within 90 seconds (gas furnace) or 2–3 minutes (heat pump). No warm air = call a service tech now while scheduling is loose.
2. Replace the filter
Fresh filter for the heating season. Same 1" filter frequency as summer isn't required in winter (you'll go 60–90 days easily), but start with a clean one.
3. Book your fall tune-up
Especially important if you have a gas furnace — combustion safety checks catch cracked heat exchangers, incorrect gas pressure, and blocked flues before they become CO events. Book in October, before first cold snap.
4. Check smoke and CO detectors
Every fall, before you start burning gas. Test buttons + fresh batteries. If your CO detector is 5+ years old, replace it (sensors degrade). $30 well spent.
5. Clear the flue vent (gas furnace)
Walk outside and confirm the furnace flue vent (short PVC pipe out the side of the house or roof) is unobstructed. Wasp nests, bird nests, and dryer-lint accumulation happen. Blocked vent = furnace lockout at best, CO risk at worst.
6. Test the auxiliary heat (heat pump)
If you have a heat pump with electric strip heat backup, verify it works. On the thermostat, force EMERGENCY HEAT mode for 10 minutes. Confirm warm air. This is what runs on the coldest nights if the primary heat pump can't keep up.
7. Reset the thermostat schedule
Program your heating schedule. Setback strategies (65°F night, 68°F day) save meaningful gas or electricity over the winter. If you have a smart thermostat, let it learn your schedule for a week.
Winter-specific things to watch for
- Cold air blowing at the start of a heating cycle — normal for the first minute (heat exchanger warming up)
- Cold air blowing throughout — bad. See Furnace Blowing Cold Air
- Rumbling or booming on furnace ignition — dirty burners or delayed ignition. Get it checked.
- Soot around registers — cracked heat exchanger. Stop using it and call.
- Persistent gas smell — leave, call SoCalGas at 1-800-427-2200 from a safe location
Book your fall tune-up — best done in October, ideally before Thanksgiving.
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