Diagnose
Engineering Troubleshooting Guides
Start from the symptom. Each guide lists the likely causes with what to check for each, a small worked calculation, and how to write a problem statement another engineer can act on.
See the guidesElectrical & Power
Why Is an Electric Motor Overheating?
The common causes of motor overheating (overload, voltage problems, poor cooling, duty, drives and bearings), what to check for each, and a worked loss calculation.
Why Does a Circuit Breaker Keep Tripping?
Overload, short circuit, ground fault, inrush, loose connections and heat: how to tell the causes apart from how and when the breaker trips.
Why Does a VFD Trip on Overcurrent or Overvoltage?
The common causes of variable frequency drive overcurrent, overvoltage and overload faults, what points to each, and what to check.
Why Is a Transformer Humming Loudly or Running Hot?
Normal hum versus abnormal noise, and the common causes of transformer overheating: overload, harmonics, poor ventilation, loose connections and voltage problems.
Why Does a GFCI Keep Tripping?
Ground-fault current, moisture, shared neutrals, damaged appliances and nuisance trips: how to tell the causes apart.
Mechanical, HVAC & Fluids
Why Is a Pump Delivering Low Flow or Making Noise?
Cavitation, air in the line, a blocked suction, a worn impeller, wrong rotation and system changes: how to separate the causes from the symptoms.
Why Is an Air Conditioner Not Cooling Enough?
Airflow, refrigerant charge, dirty coils, controls and electrical faults: how to separate the common causes of poor cooling, with the temperature-split check.
Controls & Instrumentation
Why Is a 4-20 mA Loop Reading Wrong or Stuck?
Open circuits, ground loops, insufficient supply voltage, wrong range and failed transmitters: a step-by-step way to isolate a faulty 4-20 mA loop.
Why Does a PLC Output Not Turn On the Field Device?
Logic, forced values, output module faults, blown output fuses, missing field power and wiring: a systematic way to find where the signal stops.
How these pages work
Describe the symptom
Record what happened, when, and what changed.
List the causes
Each guide ranks the usual causes and what points to them.
Check, then fix
Measurements by qualified people, following site safety rules.
Write it down
Separate what you observed from what you concluded.
Questions
Can I use these guides to work on live equipment?
They are learning material. Electrical measurements and repairs belong with qualified personnel following lockout/tagout and the site safety procedures.
Do the guides replace the manufacturer manual?
No. Limits such as temperature class and rated voltage come from the nameplate and manufacturer documents.
Educational material. Examples use simplified, hypothetical inputs and are not a design, a construction document or professional engineering advice. Confirm requirements with the codes and standards adopted where the work is built and with a licensed engineer.
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