Know Whether It's Really the Charge
Read superheat and subcooling in context, so mixed symptoms that look normal at first glance don't send you to the gauges for nothing.
System Diagnostics
Find Out Why It Runs but Won't Cool
When the unit runs but the house is still warm, ACLogics tells you what to check next until the real fault is confirmed, so you stop swapping parts on a guess.
FAULT SYMPTOM
Low suction pressure
CHECK 01
Measure Evaporator Temperature Drop (Delta-T). What is the temperature drop across the coil?
High Drop (Above 22°F)
DIAGNOSIS
Dirty air filter, closed supply registers, or low speed blower.
Low Drop (Below 16°F)
CHECK 02
Measure Superheat and Subcooling. What are your readings?
High Superheat, Low SubcoolingLow Superheat, High Subcooling
Complete diagnostic tree — every branch, every fault path
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Know what failed before you order the part.
Tell a Duct Problem From a Refrigerant Problem
Check static pressure, temperature split and fan performance in the right order, before you touch the charge.
Catch the Intermittent Electrical Fault
Work through contactor, capacitor and compressor circuits in sequence, so the fault that only shows up sometimes doesn't get away.
How a Call Goes
01
Tell It What You See
Enter the symptoms, mode, outdoor conditions and your first readings from the call.
02
Check the Fastest Things First
Get the checks in order, quickest and most telling first, so you rule causes in or out fast.
03
Show the Customer What Failed
Get a clear fix and a report that explains what failed and why, in plain words.
Frequently Asked Questions
The system cools well for 10 minutes, then supply air temperature rises. What should I check first?
Start with airflow under load before touching charge. A blower speed mismatch, dirty coil, or static-pressure issue can mimic low charge once coil temperature shifts.
I have low suction pressure but superheat is not extreme. Is this always a refrigerant shortage?
No. Metering restrictions, evaporator airflow limits, or a partially closed liquid line can produce the same pattern. Use saturation and temperature relationships together.
Head pressure is high only in the late afternoon. Is that a condenser problem or overcharge?
Treat it as a load-dependent fault first. Check condenser airflow, fan cycling logic, and coil cleanliness under peak ambient, then validate charge after airflow is confirmed.
Should technicians replace weak capacitors before measuring full operating conditions?
Measure first unless safety or startup risk demands immediate replacement. Baseline readings preserve evidence that helps confirm whether the capacitor is root cause or a secondary symptom.
Know What to Check Next on Your Next Call
Get the checks in order, confirm the cause, and fix it right the first time.