What Problem Are You Experiencing?
Select the symptom that best describes your motor issue
Motor Won't Start
No rotation, no sound, or humming only
Overheating Motor
Hot to touch, thermal trips, burning smell
VFD Keeps Tripping
Fault codes, overcurrent, overvoltage errors
Unusual Noise
Grinding, squealing, rattling sounds
Excessive Vibration
Shaking, wobbling, unbalanced operation
Low Power Output
Sluggish, can't reach rated speed/torque
Intermittent Operation
Starts then stops, random shutdowns
Bearing Problems
Hot bearings, play in shaft, metal debris
🔌 Motor Won't Start Diagnosis
CRITICAL - Equipment DownEstimated diagnosis time: 15-30 minutes
Most Common Causes:
- Failed Start Capacitor Single-phase motors - 40% of cases
- Voltage Supply Issues Blown fuses, tripped breakers - 25% of cases
- Seized Bearings/Locked Rotor Mechanical failure - 20% of cases
- Thermal Overload Tripped Previous overheating - 10% of cases
- Winding Failure Open circuit, ground fault - 5% of cases
Tools & Equipment Needed:
- Digital Multimeter (DMM)
- Clamp Ammeter
- Megohmmeter (Megger)
- Contact Thermometer
- Insulated Hand Tools
- Safety Glasses & Gloves
Verify Power Supply
What to check:
- Confirm main disconnect is ON and locked
- Check all fuses - look for blackened or blown fuses
- Test circuit breaker - should be firmly in ON position
- Measure voltage at motor terminals with DMM
Three-phase: 460-480V or 208-230V ±10%
Low voltage (<90% rated): Check utility supply or voltage drop
If voltage is correct: Proceed to Step 2
If no voltage: Check upstream power, contactors, or call electrician
Check Thermal Overload Relay
Location: Usually in motor starter or on motor terminal box
- Look for "tripped" indicator on overload relay
- Check if reset button has popped out
- Verify overload heater size matches motor FLA rating
- Allow 15-20 minutes cool-down if recently tripped
If reset and motor starts: Monitor for re-trip (possible overload condition)
If won't reset or trips immediately: Proceed to Step 3
Test Start Capacitor (Single-Phase Only)
Most common failure point in single-phase motors
- POWER OFF & LOCKED OUT
- Discharge capacitor with 20kΩ resistor across terminals (5 seconds)
- Disconnect both capacitor wires
- Visual inspection: Bulging, leaking, or burned = failed
- Test with capacitance meter: Should be within 10% of rated µF
Capacitor tests good: Proceed to Step 4
Capacitor failed: Replace and test start motor
Check for Mechanical Seizure
Test motor rotation:
- DISCONNECT POWER and verify zero voltage
- Remove drive belt or coupling (if equipped)
- Try to rotate motor shaft by hand
- Should turn smoothly with some resistance
• Rough/grinding feel = Bad bearings
• Too easy to turn = Broken or loose coupling
• Uneven resistance = Rotor dragging on stator
If shaft won't turn: Bearing replacement or motor rebuild required
If turns freely: Proceed to Step 5
Test Motor Windings
Electrical integrity test:
- Disconnect motor from power completely
- Resistance Test: Measure ohms between all wire pairs
- Three-phase: T1-T2, T2-T3, T3-T1 should be equal ±5%
- Single-phase: Measure between all terminal pairs
- Infinite resistance = Open winding (failed)
- Very low resistance = Shorted winding (failed)
- Ground Test: Measure resistance from each wire to motor frame
- Should read infinite (>10 MΩ)
- Low reading = Ground fault (dangerous!)
- Insulation Test (Megger): 500V DC test for 1 minute
- New motors: >100 MΩ
- Used motors: >5 MΩ acceptable
- <2 MΩ = Moisture or insulation failure
Test Under Load Conditions
If all tests pass but motor still won't start:
- Reconnect motor and prepare for power-on test
- Have clamp ammeter ready on one wire
- Momentarily energize motor (1-2 seconds max)
- Observe: Does shaft try to turn? Any movement?
- Measure locked-rotor current (should be 5-7x FLA)
Possible findings:
- High current, no rotation = Mechanical jam or wrong rotation
- Low/no current = Control circuit problem or starter failure
- Motor hums loudly = Single-phasing (three-phase) or capacitor issue
Need Expert Help?
Our certified technicians can diagnose and repair any motor issue. Same-day service available.
Schedule Diagnostic Visit Call Emergency Service🔥 Motor Overheating Diagnosis
WARNING - Potential DamageEstimated diagnosis time: 20-40 minutes
Most Common Causes:
- Overload Condition Running above rated capacity - 35% of cases
- Poor Ventilation Blocked fan, dirty motor - 25% of cases
- Voltage Imbalance Single-phasing, phase loss - 20% of cases
- High Ambient Temperature Inadequate cooling - 10% of cases
- Bearing Friction Worn or seized bearings - 10% of cases
Tools & Equipment Needed:
- Infrared Thermometer
- Clamp Ammeter (AC)
- Digital Multimeter
- Tachometer (RPM meter)
- Compressed Air
- Safety Equipment
Measure Motor Temperature
Take accurate temperature readings:
- Use infrared thermometer on motor frame (multiple spots)
- Measure bearing housings (both ends)
- Check terminal box area
- Measure under load conditions (motor running normally)
• Normal operating: 90-140°F (32-60°C) above ambient
• Warm but acceptable: 140-160°F (60-71°C) above ambient
• HOT - concerns: 160-180°F (71-82°C) above ambient
• DANGEROUS: >180°F (82°C) above ambient - SHUT DOWN
Motor insulation classes:
• Class B (130°C): Most common industrial
• Class F (155°C): Premium motors
• Class H (180°C): High-temp applications
Document: Record temperatures at multiple locations and operating times
Check Current Draw (Load Test)
Measure actual vs rated current:
- Locate motor nameplate - note FLA (Full Load Amps)
- Using clamp ammeter, measure current on each phase
- Take readings under normal operating conditions
- Compare to nameplate FLA rating
• >FLA = Overloaded (reduce load or upgrade motor)
• At or near FLA = Check other causes
•
Three-phase imbalance formula:
Max deviation from average ÷ average × 100 = % imbalance
Example: 52A, 48A, 50A → 50A avg → 4% imbalance (acceptable)
>10% imbalance = SERIOUS PROBLEM
Inspect Cooling System
Verify proper airflow and cooling:
- External Fan (TEFC motors):
- Remove fan cover (power OFF)
- Check fan blades for damage or debris
- Verify fan rotates freely
- Ensure fan rotates in correct direction (draws air over motor)
- Ventilation openings:
- Clean all air inlet and outlet screens
- Remove accumulated dust/dirt from motor exterior
- Check for obstructions (boxes, walls, etc.)
- Ensure 6" minimum clearance around motor
- Ambient conditions:
- Measure ambient air temperature
- Check for heat sources nearby (furnaces, hot pipes)
- Verify adequate room ventilation
Most motors rated for 40°C (104°F) ambient. For higher temperatures:
• 50°C ambient = 10% power reduction
• 60°C ambient = 20% power reduction
Consider upgrading to Class F or H insulation for hot environments.
Check Voltage Supply Quality
Measure voltage under running conditions:
- Measure voltage at motor terminals (motor running)
- Compare to nameplate voltage rating
- Check all three phases (three-phase motors)
- Calculate voltage imbalance percentage
• Optimal: Within ±5% of rated voltage
• Acceptable: Within ±10% of rated voltage
• Poor: Outside ±10% (causes overheating)
Voltage Imbalance:
Calculate same as current imbalance
• <2% = Good
• 2-5% = Investigate
• >5% = Serious problem - call electrician
Low voltage (below 90% rated) causes motor to draw excess current to maintain torque, resulting in overheating. This is common during startup of large equipment on undersized circuits.
Assess Load Conditions
Verify motor is not overloaded:
- Review application: What is motor driving?
- Check if load has changed (new equipment, process changes)
- Calculate actual load HP: HP = (Torque × RPM) ÷ 5,252
- Or estimate from current draw: HP ≈ (Volts × Amps × 1.73 × PF × Eff) ÷ 746
Many motors have service factor >1.0 (typically 1.15)
• SF 1.15 = can handle 15% overload continuously
• However, operation at SF reduces motor life
• Best practice: Operate at 75-85% of rated load
Common overload scenarios:
- Pump: Impeller wear, increased system resistance, wrong impeller
- Fan: Dampers closed, filter restriction, wrong fan curve
- Conveyor: Excess product, bearing friction, belt too tight
- Compressor: Excessive pressure, valve leaks, worn components
Bearing Inspection
Check bearing condition (often overlooked cause):
- Feel bearing housings - should be warm, not hot
- Listen for unusual noise (grinding, squealing)
- Check for excessive play in shaft (power OFF)
- Inspect for grease leakage or contamination
• Normal: 50-80°F above ambient
• Warn: 80-120°F above ambient
• Failed/Failing: >120°F above ambient
Bad bearings create friction → heat in motor
This heat conducts to windings → overheating damage
Bearing problems cause:
- 10-20°F additional motor temperature
- Increased current draw
- Reduced efficiency
- Vibration (which causes more bearing wear)
If bearings are hot or noisy: Schedule bearing replacement immediately. Bearing failure is imminent and will cause motor damage.
Overheating Can Destroy Your Motor
Don't risk expensive failure. Our thermal imaging and diagnostic tools can pinpoint the problem fast.
Schedule Inspection Emergency Service⚠️ VFD Tripping / Fault Diagnosis
CRITICAL - System DownEstimated diagnosis time: 30-60 minutes
Most Common VFD Faults:
- Overcurrent (OC) Motor overload, acceleration too fast - 30%
- Overvoltage (OV) Deceleration too fast, regeneration - 20%
- Ground Fault (GF) Cable damage, motor winding fault - 15%
- Overtemperature (OH) Inadequate cooling, ambient temp - 15%
- Undervoltage (UV) Power supply issues - 10%
- Communication Loss Control wiring, network issues - 10%
First Steps for ANY VFD Fault:
1. Record the fault code from VFD display
2. Check fault history (usually in parameters menu)
3. Consult VFD manual for specific fault code meaning
4. Note: What was motor doing when fault occurred?
5. Reset fault and observe if it immediately re-trips
• Acceleration time (P00.11 or similar): Too short = overcurrent
• Deceleration time (P00.12 or similar): Too short = overvoltage
• Motor nameplate parameters: Must match actual motor
• Output frequency limit: Should match motor rating
• Current limit: Set to 100-110% of motor FLA
Typical safe values: Accel/Decel 10-20 seconds for most applications
VFD Problems? We're VFD Specialists
We program, install, and troubleshoot all major VFD brands. Expert diagnosis and rapid repair.
VFD Services Call Now🔊 Unusual Noise Diagnosis
WARNING
Comprehensive Noise Diagnosis Guide
This diagnostic section is available in the full version of the tool. Common causes include:
• Bearing wear or failure (grinding, squealing)
• Loose mounting or coupling (knocking, rattling)
• Rotor unbalance (vibration-related noise)
• Fan blade issues (whooshing, whistling)
• Gear problems in gearbox applications
Unusual Noise? Don't Ignore It
Strange motor sounds indicate developing problems. Early diagnosis prevents catastrophic failure.
Schedule Inspection📳 Excessive Vibration Diagnosis
WARNING
Professional Vibration Analysis
This diagnostic section is available in the full version. Vibration causes include:
• Unbalanced rotor (most common - 40%)
• Misalignment between motor and load (30%)
• Loose mounting bolts or soft foot (15%)
• Bearing wear (10%)
• Bent shaft (5%)
Professional vibration analysis with accelerometers recommended for precision diagnosis.
Vibration Analysis Services
We offer professional vibration analysis and balancing services. Precision diagnosis with calibrated equipment.
Schedule Analysis⚡ Low Power Output Diagnosis
WARNING
Power Performance Testing
Full diagnostic available in complete version. Common causes:
• Low supply voltage (check under load)
• Single-phasing (three-phase motors)
• Wrong motor for application
• Worn bearings creating drag
• Partial winding failure
Requires load testing and performance measurement for accurate diagnosis.
Motor Not Performing?
Load testing and performance analysis identifies exactly what's wrong. Get your equipment back to full power.
Schedule Load Test🔄 Intermittent Operation Diagnosis
CRITICAL
Intermittent Fault Analysis
These are the hardest to diagnose. Common causes:
• Thermal cycling (overheating then cooling)
• Loose electrical connections
• Control circuit issues
• Failing contactor or starter
• Intermittent ground fault
Requires monitoring equipment and elimination testing.
Intermittent Problems? We Find Them
Our technicians use data loggers and monitoring equipment to catch elusive problems.
Schedule Diagnostic⚙️ Bearing Problem Diagnosis
CRITICAL
Bearing Analysis & Replacement
Bearing failures account for 50%+ of motor failures. Signs:
• High bearing temperature (>180°F)
• Grinding or squealing noise
• Excessive shaft play
• Grease leakage or contamination
• Vibration increase
Caught early: $200-500 repair. Ignored: $2,000-5,000+ motor replacement.
Bearing Problems? We Replace Fast
Expert bearing replacement with precision alignment. Most jobs completed in 24-48 hours.
Schedule Bearing Service
