Our team at Fast Affordable Air recently completed a detailed HVAC service on a Lennox Merit Series furnace and air conditioning system located in the attic of a Las Vegas home. This setup included a gas furnace for heating and a split air conditioner system for cooling. The homeowner reported poor cooling performance, prompting a full diagnostic inspection and repair.
Initial Diagnostic and Pressure Readings
We began the service outdoors at the condenser unit using Yellow Jacket manifold gauges to measure refrigerant pressures. The low-side (blue gauge) reading was around 75 psi, while the high-side (red gauge) was close to 250 psi. These readings suggested that the refrigerant charge was within range for R-410A refrigerant, indicating that no major leaks were present. However, we continued testing to ensure optimal efficiency and temperature split.
Electrical Component Testing
Next, we checked the electrical components inside the condenser. Using a Fieldpiece SC260 multimeter, we measured the capacitor and amperage draw. The multimeter showed 0.50 microfarads on one of the capacitors — significantly below its rated value. This confirmed a weak start capacitor, which can cause the compressor and fan motor to struggle during startup. We replaced the faulty capacitor with a new one that met manufacturer specifications.
Inspection of Attic Air Handler and Duct System
Inside the attic, the Lennox Merit Series gas furnace was inspected. The return and supply ducts were securely fastened and sealed with foil tape, and we verified that the flex duct insulation was intact. Proper sealing helps maintain efficient airflow and reduces energy loss — a key factor for HVAC efficiency.
The condensate drain line was also flushed to ensure proper water flow. Clogged drains can lead to water damage or safety switch activation that shuts down the system. The PVC drainage system was in good shape, and the slope was adequate for gravity-assisted drainage.
Refrigerant Line and Coil Condition
We inspected the copper refrigerant lines for signs of corrosion or oil residue, which could indicate leaks. The suction line had visible oxidation, but no active leaks were detected. The evaporator coil was slightly dusty — a common issue in attic systems — and was cleaned to improve heat transfer efficiency. Regular coil maintenance can prevent airflow restriction and extend system lifespan.
Performance Testing
After completing the electrical repair and coil cleaning, we restarted the system and allowed it to stabilize. The supply air temperature dropped significantly, indicating that the unit was operating efficiently again. With the capacitor replaced and all components checked, the Lennox system was performing to factory standards, restoring reliable comfort throughout the home.
Why Proper Diagnostics Matter
Accurate pressure readings and electrical measurements are essential in HVAC repair. Even a small drop in microfarads on a capacitor can cause short cycling, hard starts, or compressor failure. Similarly, maintaining clean coils and sealed ducts ensures that conditioned air reaches every room without wasting energy. These small details make a big difference in air conditioning performance — especially in the Las Vegas heat.
For homeowners, this project demonstrates how routine maintenance and professional diagnostics can prevent costly breakdowns and ensure comfort all year round.
