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HVAC Refrigeration Guide — HVAC Troubleshooting

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

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

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.

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Mitsubishi Mini-Split E6/UP: Fix Communication & Control Board Faults

Mitsubishi Mini-Split E6/UP: Fix Communication & Control Board Faults

Mitsubishi Electric MXZ systems throwing E6 or UP codes almost always point to communication wiring or the outdoor control board — not the compressor. This guide walks through the correct diagnostic sequence, explains why control boards are model-line specific, and covers outdoor fan motor failures that show up without any error code at all.

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Williams Wall Furnace Won't Light? Diagnose & Fix It

Williams Wall Furnace Won't Light? Diagnose & Fix It

Williams wall furnaces run on millivolt control — no circuit boards, no flash codes. When a pilot won't hold, the unit short-cycles, or the thermostat stops responding, the fix is almost always a single OEM part. This guide walks through the four most common failure points — spark electrode, limit switch, millivolt thermostat, and blower motor — with diagnostic steps and confirmed Williams part numbers for each.

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TXV Troubleshooting in the Field

TXV Troubleshooting in the Field

A failing TXV rarely throws a fault code — it shows up as frost on the suction line, erratic superheat, or a system that won't hold temperature no matter how much refrigerant gets added. This guide walks through the five field symptoms that point to the valve (not the charge), how to confirm a bad TXV before replacing it, and how to match the right replacement by refrigerant type and equalization style — with notes on the Danfoss 068U1839, Copeland Alco 091050, and Amana-Goodman OEM valves.

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