HVAC Refrigeration Guide

Gas Furnace Ignition Lockouts: Single-Stage vs. Staged Systems

Sep 16, 2026

Learn how to diagnose gas furnace ignition lockouts across conventional single-stage and staged or modulating systems. This guide covers igniters, flame sensors, pressure-switch interlocks, fault codes, and the testing sequence that helps prevent unnecessary parts swaps.

Tags: condensing furnace, flame sensor, furnace repair, gas furnace, heating systems, hot surface igniter, HVAC diagnostics, ignition lockout

Crankcase Heater Failure: Diagnosing Migration, Flooding & Slugging

Sep 09, 2026

A dead crankcase heater rarely announces itself — it shows up weeks later as a failed compressor. This guide helps HVACR technicians distinguish migration, flooding, and slugging, field-diagnose heater failures, and navigate new A2L system considerations for R-454B and R-32.

Tags: A2L refrigerants, compressor diagnosis, compressor flooding, crankcase heater, HVACR troubleshooting, R-32, R-454B, refrigerant migration, refrigeration service, slugging

How to Read Superheat and Subcooling Together

Sep 02, 2026

Superheat says low charge. Subcooling says overcharge. You don't have a gauge problem — you have a metering device or airflow issue. Learn how to read both numbers together using the four-quadrant diagnostic to pinpoint the real fault fast.

Tags: A2L refrigerants, fixed orifice, HVAC diagnostics, metering device, R-454B, refrigerant charging, refrigeration, subcooling, superheat, TXV

Aerco Boiler Controls: Flow Sensors, Actuators & Diagnostics

Aug 26, 2026

Aerco's modulating boiler controls require a different diagnostic approach than standard commercial boilers. This guide covers the three components behind most field failures — flow sensors, actuator assemblies, and control boards — with fault patterns, triage tables, and calibration tips for Benchmark and Innovation series units.

Tags: Actuator, Aerco, Benchmark Series, Boiler Controls, Commercial Boiler, Control Board, Flow Sensor, HVAC Diagnostics, Innovation Series, OEM Parts

AAON RTU No Heat? Diagnose Electric Heat, Inducer & Controller

Aug 23, 2026

Most AAON RTU no-heat service calls trace back to one of three failure points: an open electric heating element, a worn draft inducer that can't close the pressure switch, or a controller that won't communicate. This guide walks through how to confirm which failure you're actually dealing with — before you order a part.

Tags: AAON, Controller Diagnostics, Draft Inducer, Electric Heat, Heating Element, HVAC Troubleshooting, OEM Parts, Pressure Switch, Rooftop Unit, RTU