Written by technicians for technicians. Systematic diagnosis for the calls that matter — offline, in the field, when it counts.
Pressure switch faults are the #1 misdiagnosed furnace call. Systematic diagnosis — inducer motor to condensate drain — before condemning any part.
Reversing valve diagnosis, defrost cycle faults, low charge in heating mode, and auxiliary heat sequencing — step by step.
Mitsubishi, Daikin, Gree, LG, Pioneer — every brand uses different code systems. What codes mean and how to find what applies.
Target values matter more than actual readings. Fixed orifice vs TXV systems, calculating targets, and what abnormal readings indicate.
Navien E003, E012, E016 and Rinnai error codes explained. Ignition failures, flame loss, and venting faults on the two most common brands.
High static pressure is the most under-diagnosed problem in residential HVAC. How to measure TESP, interpret results, and find the root cause.
Compressor replacement is expensive. Every test to run before condemning — capacitor, winding tests, hard start, pump-down.
Hydronic systems fail differently than forced-air. Low water cutoff, zone valve faults, ignition sequence troubleshooting.
R-454B is replacing R-410A. A2L handling requirements, safety considerations, charging procedures, and tool compatibility.
Wire colors aren't always standardized — assuming they are leads to callbacks. Conventions, exceptions, and how to verify on unfamiliar systems.
Fieldmode works fully offline. Guided trees, P-T charts, error codes, and more — free to use.
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