When you sell, the buyer’s home inspector will run the heat, open the furnace closet, read the equipment labels and write down what they see. In Daly City and South San Francisco that usually means a gas furnace in the garage, often next to the water heater, and sometimes an air conditioner or heat pump outside. The report goes to the buyer, and what it says can turn into repair requests or a price discussion. Checking the system yourself a few weeks before listing lets you decide, on your own schedule, what to fix, what to disclose and what to leave to the buyer.
What a buyer’s inspector usually looks at
A general home inspection is visual. The inspector does not take the furnace apart. Expect them to:
- run the heat from the thermostat and confirm warm air reaches the rooms;
- read the data plate on the furnace and outdoor unit to estimate their age;
- look at the vent pipe and its connection to the furnace, the gas shutoff and the flexible gas connector;
- note rust, soot, scorch marks or water stains around the equipment;
- check the filter, any visible ducts and the condensate line on high-efficiency equipment;
- look for working smoke and carbon monoxide alarms and at how the water heater is braced.
Many inspectors will not run an air conditioner on a cool day, because running one in cold weather can harm the compressor, so the report may list it as not tested. When anything looks wrong, the usual line is a recommendation for further evaluation by an HVAC contractor, and the buyer will then ask for exactly that.
What a pre-listing HVAC check covers
A technician goes further than the home inspector:
- Combustion and carbon monoxide. Flue draft, CO in the exhaust and around the furnace, and the condition of the vent from the garage up to the roof.
- The heat exchanger, as far as it can be seen with the burners out or with a camera.
- Ignition and safety controls, the flame sensor and the limit and pressure switches.
- Airflow. Filter, blower, temperature rise across the furnace and leaks in the ducts and returns in the garage.
- Cooling equipment, run if the weather allows, with the outdoor coil checked for salt-air corrosion.
- The thermostat and its wiring.
You get a written summary of what was found and, for anything that needs work, a written estimate before any work begins. A furnace maintenance visit covers most of this list and leaves a dated service record to hand to the buyer.
Fix, disclose or credit
| Finding | Usual approach | Why |
|---|---|---|
| Gas, vent or CO problem, suspected cracked heat exchanger | Stop using the furnace and fix it before listing | Safety comes first, and it will be found anyway |
| Old uncoated brass gas connector, missing CO alarm, unbraced water heater | Fix | Small jobs that inspectors commonly flag |
| Dirty filter, dusty registers, overdue service | Do it | Cheap, and the system looks cared for |
| Old furnace that works well | Disclose the age, share the records | A rushed replacement is rarely what the buyer would have chosen |
| Failed or failing major part | Get a written estimate, then repair or offer a credit | A real number replaces the buyer’s worst-case guess |
| Rusted outdoor unit | Have it cleaned and serviced, note its condition | Salt-air wear is visible and better explained than discovered |
If a cracked heat exchanger is suspected, do not restart the furnace until it has been checked; our page on a cracked heat exchanger explains why. For a major part on older equipment, the repair-or-replace guide walks through how to weigh the two, and furnace repair covers the work itself.
Disclosure
California sellers must disclose known material facts about the property in writing, and the standard disclosure form asks about the heating, air conditioning and related systems. Write down what you know: a furnace that has had repeated repairs, a recurring problem, an air conditioner you never use and cannot vouch for. California also requires carbon monoxide alarms in homes with gas appliances or an attached garage, and a braced water heater. Your agent handles the forms; this guide is not legal advice. The practical point is simple: a problem you disclosed is a line in the paperwork, while one the buyer finds can reopen the price.
Records worth gathering
- Service receipts for the last few years, with dates.
- The installation date of each piece of equipment, if it is not on the data plate.
- Permit records for past furnace or AC replacements. Replacements normally need a permit; if one was done without, talk to your agent about how to handle it.
- Warranty papers. Some manufacturer warranties can pass to a new owner, sometimes only if registered.
- The filter size, written on the furnace cabinet, which the next owner will thank you for.
What buyers here tend to notice
Many homes on the fog side have heat and no central air, so buyers mainly want to see a furnace that lights cleanly, runs quietly and is reasonably young or well kept. In a mid-century house with the furnace in the garage they will look at the vent, the gas connector and the water heater next to it; our mid-century home guide covers that layout. A musty garage, water stains under windows or a musty smell when the heat starts raise questions about damp, so deal with the source before the open house. Outdoor units near the coast show salt wear early, and a clean, serviced unit answers that question before it is asked.
Timing
Book the check three to six weeks before listing photos. That leaves time for parts to arrive, for any permit, and for a second visit if needed, and it puts dated receipts in your disclosure packet before the buyer’s inspector arrives.