Your mother's furnace does not need you to think about it until the morning it stops. The filter clogs slowly, the service visit gets missed quietly, and then one cold night the house is colder than it was and you learn about it from a phone call. The fix is not complicated. It is just owned.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Name the filter first
Look at the furnace or the return grille where the filter slides in. The size is usually printed on the frame edge. Write it on a card taped inside a closet door and on the first page of your folder. Note the arrow on the filter, which shows the airflow direction. A filter bought at the wrong size can leave gaps, and the card is what a neighbor or helper will need.
Decide who buys and who swaps. The options are a supply delivered to the house, a local helper who changes it on a visit, or a standing order you set up yourself. Pick one and write it down. 'Someone will do it' is how filters stay in place for far too long.
Own the service visit
Many heating systems are serviced once a year, usually before the heating season. Check whether there is a service contract, which company holds it, and whose name is on the account. If the account is still in your mother's name and she no longer answers calls, ask the company what the account holder must authorize and whether you can be added as a contact.
Ask the technician to write down the filter size, any age or model details on the unit, and anything they recommend. Keep that sheet. The next technician will ask for it.
Plan the no-heat call
When heat stops, the first call is usually the service company. The second may be the utility company's emergency line, which is printed on the bill. The third is whoever can get into the house. Put all three numbers on one sheet near the thermostat. Include where the gas shutoff is if the home uses gas, and who in town knows how to reset the switch. Do not expect your mother to troubleshoot by phone.
Also ask a local helper to know where the thermostat is and what setting is wanted when no one is home. Some people turn it down by accident, and some switch it off at night. Name which one is wanted.
Tonight
Find the filter size on the frame and write it down. Check whether the account and any service contract are in your name or hers. Save the service company and utility emergency numbers in your phone and on paper in the house. If you do not know who services the unit, look for a sticker or an old invoice near the furnace, or ask a local helper to photograph the label and send it to you.
What to tell the doctor
If your mother has been wearing extra layers indoors, has complained about being cold, or seems less active in the house, tell her doctor. The doctor can decide whether any of that matters for her health. The furnace schedule is yours to manage.
For more on keeping a St. Louis home running from far away, see Local Help for a St. Louis Parent.