Most HVAC contractors offer separate furnace tune-ups and AC tune-ups as two distinct service calls. We combine them in a single scheduled visit that covers both systems completely, for one practical reason: the measurements from one side of the system inform the other. A technician who has just measured 0.68″ WC total external static pressure on the furnace side knows before touching the AC system that the high static will reduce delta-T across the evaporator coil and produce misleading refrigerant charge readings if not accounted for. A technician coming to service only the AC system has none of that context.
The combined HVAC tune-up is scheduled in spring (April–May), covering the AC system before summer demand arrives and documenting the furnace’s end-of-season condition before the shoulder months when parts lead times are manageable and schedules are available. For homeowners who prefer fall scheduling, we offer the combined visit in September–October with the heating side receiving primary attention before the November heating season and the cooling side documented for the record after a full summer of operation.
The technician checks the air filter first, before any instrument readings. A severely restricted filter creates conditions that produce misleading measurements on both the heating and cooling sides — high limit trips that look like failed limit switches, high superheat that looks like a refrigerant charge problem, high static pressure that looks like a duct problem. If the filter is past its service life, it is replaced before measurements begin so that the readings reflect system condition rather than filter condition. We document the filter’s condition at arrival and the action taken in the service report.
The furnace is run to steady state and combustion analysis is performed with a Testo 320 Basic flue gas analyzer. We record CO air-free (target under 100 ppm; action threshold 200 ppm triggers shutdown and investigation), O₂ percentage (target 5–9%), and stack temperature versus manufacturer specification. For two-stage and modulating furnaces, we run the analysis at each firing stage — a furnace with clean combustion at high fire and elevated CO at low fire has a different diagnosis than one with elevated CO at all stages. For SunCrest and Traverse Ridge addresses, we verify that the altitude derate has been performed by comparing the measured manifold pressure against the manufacturer’s altitude-corrected target. If the derate was not performed, we correct it during the visit and rerun the combustion analysis to confirm correction.
Incoming line pressure measured at the gas valve inlet (target 7″ WC on Dominion Energy residential supply). Manifold pressure measured at the gas valve outlet and compared against the altitude-corrected specification for the furnace model and installation elevation. Both pressures are documented in the service report.
Flame sensor removed, cleaned with fine steel wool or emery cloth, and measured for flame current output with a microamp meter in the furnace door service circuit. Target: 1.5–5 microamps on a clean sensor in a properly burning furnace. We document the reading before and after cleaning. A sensor that reads below 0.5 microamps after cleaning is replaced. At SunCrest and Traverse Ridge addresses with altitude-derate histories, we flag sensors reading below 0.8 microamps after cleaning as borderline — a sensor at 0.7 microamps in April is approaching the failure threshold by January under normal heating-season carbon accumulation.
Visual inspection and resistance measurement. Silicon carbide igniters: resistance above 100Ω indicates a degraded element. Silicon nitride igniters: open circuit test. Borderline igniters identified in April get replaced proactively before the heating season rather than reactively on a January no-heat call.
Condensate trap and drain line flushed with compressed CO₂ or compressed nitrogen. Drain flow confirmed at the terminus. Descaling agent applied to inhibit calcium carbonate scale re-deposition through the heating season. Drain pan tablets placed where accessible. At south Salt Lake Valley water hardness of 15–25 grains per gallon, this step is among the most consequential in the tune-up — a blocked condensate drain is the single most common cause of furnace no-heat calls in the November–February period on condensing furnaces in our service area.
Amperage measured against nameplate FLA. Bearing condition checked by listening for vibration during operation and manually checking shaft play with power disconnected. An inducer motor drawing above FLA or showing shaft bearing roughness gets a replacement recommendation with cost estimate documented in the service report.
Visual inspection of accessible heat exchanger surfaces at the burner access panel. For furnaces over 12 years old, or where the combustion analysis shows any CO elevation above the target range, we use a borescope for a full cell-by-cell inspection. Heat exchanger inspection findings are documented with photos where concerns are noted. A clean inspection on a furnace over 12 years old is explicitly documented as such in the service report — this protects homeowners from uninvestigated condemnation quotes by other contractors in subsequent years.
Blower motor amperage against nameplate FLA. Blower wheel debris inspection (a dirty blower wheel adds static pressure and motor load simultaneously). Contactor face inspection on older systems that retain a contactor in the control circuit. Low-voltage thermostat wiring connections at the control board checked for corrosion and loose connections.
Total external static pressure measured across the air handler. Target under 0.5″ WC. High static findings are documented with a preliminary cause assessment and follow-up recommendation. High static identified on the heating side guides the interpretation of cooling-side measurements that follow.
Supply air temperature at the supply plenum minus return air temperature at the return plenum. Target within the manufacturer’s rated temperature rise range (typically 35–65°F for 80% AFUE; 25–55°F for 96%+ AFUE). Temperature rise outside spec indicates a static pressure or gas pressure issue that requires correction before the heating season.
Dual-run capacitor measured for microfarad output on both the compressor and fan sides using a dedicated capacitor tester. Replacement threshold: below 90% of nameplate on either side is flagged; below 80% is recommended for immediate replacement. At SunCrest, Corner Canyon, and South Mountain installations where condensers operate at elevated ambient and the Arrhenius thermal degradation rate is approximately double the rate at valley-floor installations, we track capacitor replacement history in the customer file and flag units approaching the high-ambient projected replacement window.
Condenser coil inspected for debris accumulation. Cleaned if needed using low-pressure rinse from the inside out. In the south Salt Lake Valley, primary condenser coil fouling sources are cottonwood seed (May–June), construction debris in developing Herriman and South Jordan subdivisions, and fine particulate deposited during PCAPS winter inversion events. A condenser coil with 20% fin channel blockage is operating at approximately 12–15% reduced heat rejection capacity.
Evaporator coil face inspected for biological growth, debris accumulation at filter bypass points, and evidence of freeze-thaw cycles from prior undercharge events. Condensate drain line flushed and flow confirmed. Drain pan condition documented. For homes in Daybreak, Rosecrest, and newer Herriman construction where formicary corrosion on copper evaporator coils is a documented risk, we note the coil material and age in the service report and inspect the coil face for early corrosion signs.
Superheat and subcooling measured at actual outdoor ambient temperature on the day of the visit. Target: superheat 8–12°F for fixed-orifice systems; subcooling 10–15°F for TXV systems. Low superheat or subcooling outside the target range triggers a refrigerant leak search before any refrigerant is added. We do not top off refrigerant without locating and repairing the leak.
Compressor amperage against nameplate RLA. Condenser fan motor amperage against nameplate FLA. Both measured with a clamp meter and documented in the service report. A compressor drawing significantly above RLA with correct refrigerant charge and clean condenser coil has an internal mechanical problem developing; a fan drawing above FLA with a clean blade typically indicates bearing wear.
Contactor face inspection for pitting and carbon tracking (photographed and documented). Disconnect box inspection for corrosion and evidence of overheating. Low-voltage wiring connections at the condensing unit terminals. For communicating systems (Carrier Infinity, Trane ComfortLink II, Lennox iComfort S30), we check for firmware update alerts and confirm all equipment communication links are error-free.
Thermostat calibration verified against measured return air temperature and room temperature probe. All operating modes tested (heat, cool, fan, emergency heat where applicable). Staging operation confirmed on two-stage and variable-capacity systems. Outdoor temperature sensor function verified on systems with outdoor reset or demand-controlled operation.
After all component checks are complete, the system is run through a full 15–20-minute cooling cycle (or heating cycle for fall scheduling) and the delta-T across the evaporator coil (target 16–22°F for cooling) or temperature rise across the heat exchanger (target within manufacturer’s rated range for heating) is measured to confirm that all individual component checks produce a system performing correctly at the system level.
Every combined HVAC tune-up produces a single service report covering both systems, documented with all instrument readings. The heating system section includes: filter condition, combustion analysis readings (CO air-free, O₂, stack temperature), gas pressures (incoming line and manifold), flame sensor microamp before and after cleaning, igniter resistance, condensate drain flush status, inducer motor amperage, heat exchanger visual inspection finding, blower motor amperage, static pressure, and temperature rise. The cooling system section includes: capacitor microfarad readings versus nameplate (both sides), condenser coil cleaning status, evaporator coil condition, refrigerant charge (superheat and subcooling), compressor and fan motor amperages, contactor condition, and delta-T. Any findings outside acceptable range are documented with recommended action and estimated cost. The report is provided to the homeowner at the visit and retained in the customer file for manufacturer warranty compliance.
Spring window (April–May) is optimal for covering the cooling system before summer demand and documenting the furnace before the September fall tune-up window becomes fully booked. Fall window (September–October) is optimal for furnace-first scheduling before the heating season and documenting the AC system after its final summer of operation. We schedule combined tune-ups in both windows — the spring visit and the fall visit together constitute the twice-per-year maintenance recommended for south Salt Lake Valley homes above 5,000 feet elevation.
Schedule your combined HVAC tune-up for April or May to cover both systems before peak demand. We serve Draper, Sandy, Bluffdale, Riverton, South Jordan, and Herriman — dispatched from Business Park Drive with 24/7 emergency coverage.