Heating Maintenance & Tune-Ups
A Los Angeles furnace runs a fraction of the year. That long dormancy is exactly why it fails on the first cold night — and why a tune-up here is a set of measurements against published standards, not a can of compressed air.
Temperature Split: 25°F to 65°F
Temperature split is the difference between the air your furnace pulls in and the air it pushes out. For a forced air furnace, it should land between 25°F and 65°F.
We measure it properly: probes inserted into the return register and the supply register nearest the air handler, seated inside the boot rather than resting on the grille, with the system in full heating and allowed to reach steady state.
One number, taken correctly, tells us whether your problem is combustion or airflow — and those have completely different fixes.
Slow heating and excess energy use
Cause: burner settings or insufficient gas flow.
Fix: tuning the burners. This is a calibration problem, not a parts problem — which is why it so often goes undiagnosed. The house still gets warm eventually, so nobody investigates.
Very hot supply air, uneven rooms
Cause: low airflow. Hot supply temperatures increase stratification and widen the gap between rooms.
Fix: restoring airflow — repairing or replacing restrictive duct runs, reconfiguring the filter or housing, adding or enlarging a return duct, or simply opening supply registers that were closed off.
Static Pressure Is Your System's Blood Pressure
Total external static pressure measures how hard your system has to fight to move air. We take it in two places — the return plenum and the supply just ahead of the coil — with the system running at full speed, drilling and then plugging test ports if none exist.
High static pressure produces lower system airflow and higher fan energy use. It is caused by poor duct design or installation, crushed and crimped runs, undersized or dirty filters, and closed supply registers. And it is fixable: repairing duct sections, reconfiguring filter housings, adding a return or increasing its size, opening registers.
In a dry climate like California's, higher airflow is better. Low airflow costs you capacity, efficiency, and comfort simultaneously.
What we hand you afterward
Every measurement gets recorded and left with you, so next year's reading has something to be compared against. A tune-up you cannot verify is a tune-up you have to take on faith.
"I closed the vents in the rooms we don't use."
This is the most common energy-saving attempt we encounter, and it reliably creates the fault it is meant to avoid. Closing supply registers raises static pressure and cuts system airflow. Reduced airflow drives temperature rise up, and the high limit switch responds by shutting the furnace down mid-cycle to protect the heat exchanger.
The customer's experience is a furnace that "started acting up for no reason." The actual sequence started at the register. If there are rooms you genuinely do not use, the answer is zoning or a distribution redesign — multi-split systems handle this natively — not closed vents.
The Full Inspection Scope
A maintenance visit should follow a detailed written check-off list. Here is ours, in the order a technician works through it.
Structure & Cabinet
- ● Furnace frame condition and integrity
- ● Sagging or shifting on suspended and hanging units
- ● Rust or corrosion, particularly beneath the exhaust vent
- ● Condensate drain line and trap on condensing furnaces
Controls & Electrical
- ● All electrical connections inspected and secured
- ● Incoming line voltage and 24V control voltage verified
- ● Thermostat operation and programming reviewed
- ● Main blower amperage draw measured
Combustion & Heat Exchanger
- ● All flames steady, straight, and correctly colored
- ● No flame impingement on the heat exchanger
- ● Heat exchanger inspected with a light once the flame is off
- ● Gas line leak check and valve open/close verification
- ● Incoming and manifold gas pressure measured
Airflow & Distribution
- ● Air filter condition, size, and fit
- ● Blower compartment condition, blower and motor sound check
- ● Total external static pressure measured at return and supply
- ● Temperature rise measured and compared to rating plate
- ● Adjacent ductwork inspected for leaks and restriction
Venting
- ● Exhaust vent condition, leaks, rust, and corrosion
- ● Vent termination above the roofline verified
- ● Nearby fresh air intakes checked for exhaust re-entry
Operating Sequence
- ● Full start-up cycle initiated and monitored from the thermostat
- ● Several minutes allowed for the system to stabilize before measuring
- ● Inducer motor and blower checked by sound through the cycle
- ● Full shut-down cycle monitored to confirm correct sequencing
We Look Past the Equipment
Your furnace lives inside a building. Several of the biggest heating losses in a Los Angeles home are not in the furnace at all.
Attic Insulation
We assess R-value and condition. Below R-19 and in good shape, we recommend adding. Trampled, water damaged, or rodent infested to the point the R-value cannot be assessed, it should be replaced at R-30 or higher — with the ceiling air sealed from the attic side first.
Duct Insulation
Ducts running through a vented attic lose heat continuously. We inspect insulation and vapor barrier condition on all accessible ductwork, looking for tears, gaps, age degradation, and rodent damage.
Duct sealing & replacement →Thermostat Configuration
We check sensor calibration, review your actual programming against how you really use the house, and offer to reprogram it with you. Most thermostats in service are running settings nobody chose deliberately.
One Visit, or Every Season
A single pre-season tune-up catches what dormancy caused. A maintenance plan gives you a year-over-year record of the same measurements, which is how you spot a system drifting out of spec before it fails.
See the maintenance plan →What maintenance is actually looking for
Combustion safety is the part that matters most, and the part you cannot check yourself.
How to Tell If Your Furnace Is Producing Carbon Monoxide
The warning signs of a carbon monoxide leak, and which ones mean leave the house now.
Read the article →Why Does My Furnace Keep Shutting Off After a Few Minutes?
A furnace that starts then quits after a few minutes is usually protecting itself from something.
Read the article →What Size Furnace Do I Need? Why Bigger Is Never Better
An oversized furnace costs more, wears out faster and heats less evenly. Here is why.
Read the article →Tune-Up FAQs
What is a temperature split and what should mine be?
It is the difference between the air entering your return and the air leaving your supply register. For a forced air furnace it should fall between 25°F and 65°F. We measure it with probes placed inside the register boots, not on the grilles, after the system has reached steady state in full heating.
What does it mean if my temperature split is too low?
Your furnace is heating slowly and burning more energy than it should. The usual causes are burner settings or insufficient gas flow, and the fix is tuning the burners rather than replacing parts. Low split is easy to miss because the house does eventually get warm, just expensively.
What does it mean if my temperature split is too high?
Supply air is coming out very hot, which increases stratification and widens temperature differences between rooms. The cause is almost always low airflow. Fixes include repairing or replacing restrictive ducts, reconfiguring the filter or its housing, adding or enlarging a return duct, and opening closed supply registers.
What is static pressure and why do you measure it?
Total external static pressure measures how restrictive your system is to airflow. We measure it in the return plenum and in the supply just before the coil, with the system running at full speed. High static pressure means reduced airflow and higher fan energy, and it is the root cause behind a large share of heating complaints.
Does closing vents in unused rooms save money?
No, and it actively causes faults. Closing supply registers raises static pressure and reduces system airflow. That drives temperature rise up and commonly trips the high limit switch, which shuts the furnace down mid-cycle. If certain rooms are unused, the answer is zoning or a system design change, not closed vents.
How often does a furnace really need service?
Annually, and in Los Angeles the timing matters more than most places. Furnaces here sit unused for the majority of the year, so the first cold night is effectively a cold start after eight or nine months idle. A pre-season inspection catches the failures that dormancy causes before you need the heat.
What do you actually check during a heating tune-up?
A written checklist covering the frame and cabinet, all electrical connections and voltages, a full monitored start-up and shut-down cycle, measured temperature rise, burner flame quality and heat exchanger inspection, gas line and pressure verification, exhaust vent condition and termination, filter, and blower amperage.
Book It Before the First Cold Night
The busiest heating day of the year in Los Angeles is the first genuinely cold evening. Everyone discovers the problem at the same moment. Get ahead of it.